Showing papers on "Complementary DNA published in 1982"
TL;DR: The cloning procedure described here mitigates this shortcoming by attributing the high efficiency of cloning full- or nearly full-length cDNA to the fact that the plasmid DNA vector itself serves as the primer for first- and second-strand cDNA synthesis.
Abstract: A widely recognized difficulty of presently used methods for cDNA cloning is obtaining cDNA segments that contain the entire nucleotide sequence of the corresponding mRNA. The cloning procedure described here mitigates this shortcoming. Of the 10(5) plasmid-cDNA recombinants obtained per microgram of rabbit reticulocyte mRNA, about 10% contained a complete alpha- of beta-globin mRNA sequence, and at least 30 to 50%, but very likely more, contained the entire globin coding regions. We attribute the high efficiency of cloning full- or nearly full-length cDNA to (i) the fact that the plasmid DNA vector itself serves as the primer for first- and second-strand cDNA synthesis, (ii) the lack of any nuclease treatment of the products, and (iii) the fact that one of the steps in the procedure results in preferential cloning of recombinants with full-length cDNA's over those with truncated cDNA's.
1,333 citations
TL;DR: The nucleotide sequence of cloned cDNA for preproenkephalin from bovine adrenal medulla indicates that the precursor protein contains four copies of Met-enke PHalin, a previously undetected opioid peptide.
Abstract: The nucleotide sequence of cloned cDNA for preproenkephalin from bovine adrenal medulla indicates that the precursor protein contains four copies of Met-enkephalin and one copy each of Leu-enkephalin, Met-enkephalin-Arg6 -Phe7 and Met-enkephalin-Arg6 -Gly7 -Leu8, a previously undetected opioid peptide. The enkephalin and extended enkephalin sequences are each bounded by paired basic amino acid residues. Preproenkephalin may represent a multi-hormone precursor, like the corticotropin-β-lipotropin precursor.
885 citations
TL;DR: cDNA clones corresponding to a mRNA whose level is rapidly increased by addition of oestradiol to the culture medium have been isolated by differential screening of a cDNA library from the breast cancer cell line MCF-7, which contains oestrogen receptors.
Abstract: cDNA clones corresponding to a mRNA whose level is rapidly increased by addition of oestradiol to the culture medium have been isolated by differential screening of a cDNA library from the breast cancer cell line MCF-7, which contains oestrogen receptors. Such clones will be useful in studies of the DNA sequences required for hormonal induction and to determine whether expression of the corresponding gene is in any way related to the cancerous state. We have also obtained a cDNA clone for a messenger whose level is apparently decreased by steroid hormones.
743 citations
TL;DR: The primary structure of a precursor protein that contains β-neo-endorphin, dynorphin and a third leucine-enkephalin sequence with a carboxyl extension has been deduced from the nucleotide sequence of cloned DNA complementary to the porcine hypothalamic mRNA encoding it.
Abstract: The primary structure of a precursor protein that contains beta-neo-endorphin, dynorphin and a third leucine-enkephalin sequence with a carboxyl extension has been deduced from the nucleotide sequence of cloned DNA complementary to the porcine hypothalamic mRNA encoding it. The three peptides are each bounded by Lys-Arg. This precursor protein, like adrenal preproenkephalin and the corticotropin/beta-lipotropin precursor, comprises multiple repetitive units and a cysteine-containing amino-terminal sequence preceded by a signal peptide.
735 citations
TL;DR: The polypeptide produced through expression of this DNA sequence in Escherichia coli or cultured monkey cells had properties characteristic of authentic human IFN-γ.
Abstract: A cDNA sequence coding for human immune interferon (IFN-γ) has been identified in a cDNA library prepared from gel-fractionated IFN-γ mRNA. The DNA sequence codes for a polypeptide of 166 amino acids, 20 of which could constitute a signal peptide. The polypeptide produced through expression of this DNA sequence in Escherichia coli or cultured monkey cells had properties characteristic of authentic human IFN-γ.
702 citations
TL;DR: DNA sequences complementary to the Torpedo californica electroplax mRNA coding for the α-subunit precursor of the acetylcholine receptor were cloned and indicated that the precursor consists of 461 amino acids including a prepeptide of 24 amino acids.
Abstract: DNA sequences complementary to the Torpedo californica electroplax mRNA coding for the α-subunit precursor of the acetylcholine receptor were cloned. The nucleotide sequence of the cloned cDNA indicates that the precursor consists of 461 amino acids including a prepeptide of 24 amino acids. Possible sites for acetylcholine binding and antigenic determinants on the α-subunit molecule are discussed.
683 citations
TL;DR: A novel approach has been developed for the preparation of highly radioactive, strand-specific M13 probes by using a universal primer to initiate the DNA synthesis of the complementary strand of the M13 sequence downstream from the inserted sequence.
526 citations
TL;DR: It is concluded that plasmid DNA integrated into Chinese hamster ovary DNA is extremely fluid, as demonstrated by its frequent deletion, and transfected DNA sequences most frequently deleted are also those most frequently amplified on methotrexate selection.
523 citations
TL;DR: The sequence of a cDNA encoding the nonapeptide arginine vasopressin (A VP) and its carrier protein, neurophysin II (NpII) from bovine hypothalamus, proves that the 166-amino acid precursor molecule contains a signal peptide of 19 amino acids followed directly by A VP connected to NpII by a Gly-Lys-Arg sequence.
Abstract: The sequence of a cDNA encoding the nonapeptide arginine vasopressin (A VP) and its carrier protein, neurophysin II (NpII) from bovine hypothalamus, proves that the 166-amino acid precursor molecule contains a signal peptide of 19 amino acids followed directly by A VP connected to NpII by a Gly-Lys-Arg sequence. The carboxy-terminal region of the precursor contains a naturally occurring glycopolypeptide of 39 amino acids which is separated from NpII by a single arginine residue.
517 citations
TL;DR: All the evidence to date and the present data suggest that this is the only gene for IFN-γ and that the resolution of IFn-γ into two components18 is probably the result of post-translational processing of the protein.
Abstract: Sequence determination of cloned cDNAs and genes of the three classes of interferon (IFN-alpha, -beta and -gamma) has revealed more than a dozen members of the human IFN-alpha gene family and a single gene for IFN-beta. These genes are found on chromosome 9 and contain no introns. We recently reported that the 146-amino acid sequence of mature IFN-gamma deduced from the nucleotide sequence of a cloned cDNA was quite unrelated to those of the other IFNs, and that the gene for IFN-gamma contains at least one intron. We now describe the isolation, characterization and DNA sequence of the human IFN-gamma gene. It contains three introns, a repetitive DNA element, and is not highly polymorphic. All our evidence to date and the present data suggest that this is the only gene for IFN-gamma and that the resolution of IFN-gamma into two components is probably the result of post-translational processing of the protein.
489 citations
TL;DR: Five overlapping cDNAs bearing sequences specific for the human pro alpha 1(I) collagen chain are cloned for the first time and cover from residue 247 in the alpha chain to part of the 3' end untranslated region of the proalpha 1( I) mRNA for a total of 3400 nucleotides.
Abstract: We report the cloning of five overlapping cDNAs bearing sequences specific for the human pro alpha 1(I) collagen chain. Poly-A RNA enriched for collagen sequences was purified from normal human fibroblasts and used as template to synthesize double stranded cDNA. The cDNA was inserted into the Eco RI site of pBR 322 by blunt-ending and dG:dC tailing. The clones were screened by colony hybridization using the original RNA population and the resulting five positive clones subjected to restriction endonuclease mapping analysis and DNA sequencing. These overlapping clones cover from residue 247 in the alpha chain to part of the 3' end untranslated region of the pro alpha 1(I) mRNA for a total of 3400 nucleotides.
TL;DR: A cDNA library prepared from human liver has been screened for factor IX, a clotting factor that participates in the middle phase of blood coagulation and the homology in the amino acid sequence between human and bovine factor IX was found to be 83%.
Abstract: A cDNA library prepared from human liver has been screened for factor IX (Christmas factor), a clotting factor that participates in the middle phase of blood coagulation. The library was screened with a single-stranded DNA prepared from enriched mRNA for baboon factor IX and a synthetic oligonucleotide mixture. A plasmid was identified that contained a cDNA insert of 1,466 base pairs coding for human factor IX. The insert is flanked by G-C tails of 11 and 18 base pairs at the 5' and 3' ends, respectively. It also included 138 base pairs that code for an amino-terminal leader sequence, 1,248 base pairs that code for the mature protein, a stop codon, and 48 base pairs of noncoding sequence at the 3' end. The leader sequence contains 46 amino acid residues, and it is proposed that this sequence includes both a signal sequence and a pro sequence for the mature protein that circulates in plasma. The 1,248 base pairs code for a polypeptide chain composed of 416 amino acids. The amino-terminal region for this protein contains 12 glutamic acid residues that are converted to gamma-carboxyglutamic acid in the mature protein. These glutamic acid residues are coded for by both GAA and GAG. The arginyl peptide bonds that are cleaved in the conversion of human factor IX to factor IXa by factor XIa were identified as Arg145-Ala146 and Arg180-Val181. The cleavage of these two internal peptide bonds results in the formation of an activation peptide (35 amino acids) and factor IXa, a serine protease composed of a light chain (145 amino acids) and a heavy chain (236 amino acids), and these two chains are held together by a disulfide bond(s). The active site residues including histidine, aspartate, and serine are located in the heavy chain at positions 221, 270, and 366, respectively. These amino acids are homologous with His57, Asp102, and Ser195 in the active site of chymotrypsin. Two potential carbohydrate binding sites (Asn-X-Thr) were identified in the activation peptide, and these were located at Asn157 and Asn167. The homology in the amino acid sequence between human and bovine factor IX was found to be 83%.
TL;DR: The data suggest that gene duplication and deletion presumably by homologous but unequal crossing-over has altered the size and organization of the class I clusters in different mouse strains and probably is an important mechanism for generating polymorphism in these genes.
TL;DR: The amino acid sequence homology observed between preproenkephalin B and preproinjector A suggests that the two genes have been generated from a common ancestor by gene duplication.
Abstract: The primary structure of porcine preproenkephalin B has been elucidated by cloning and sequencing cDNA: it contains neoendorphin, dynorphin and leumorphin (containing rimorphin as its amino-terminus). These opioid peptides, each having a leucine-enkephalin structure, act on the kappa-receptor. We have now cloned a human genomic DNA segment containing the preproenkephalin B gene. The structural organization of this gene resembles those of the genes encoding the other opioid peptide precursors, that is, preproenkephalin A and the corticotropin-beta-lipotropin precursor (ACTH-beta-LPH precursor). The primary structure of human preproenkephalin B has been deduced from the gene sequence. The amino acid sequence homology observed between preproenkephalin B and preproenkephalin A, together with the similarity between their gene organizations, suggests that the two genes have been generated from a common ancestor by gene duplication.
TL;DR: A cluster of amino acid changes is located in the viral coat proteins, especially in the NH2-terminal half of the viral capsid protein VP1, which may imply that the mutations in the VP1 coding region contribute to attenuation.
Abstract: The complete nucleotide sequence of the genome of the type 1 poliovirus vaccine strain (LSc,2ab) was determined by using molecular cloning and rapid sequence analysis techniques. The restriction fragments of double-stranded cDNA synthesized from the vaccine strain RNA were inserted into the adequate sites of cloning vector pBR322. Sequence analysis of the cloned DNAs revealed that the virion RNA molecule was 7,441 nucleotides long and polyadenylylated at the 3' terminus. When the nucleotide sequence was compared with that of the genome of the virulent parental strain (Mahoney), 57 base substitutions were observed to be scattered all over the genome. Of these, 21 resulted in amino acid changes in a number of viral proteins. A cluster of amino acid changes is located in the viral coat proteins, especially in the NH2-terminal half of the viral capsid protein VP1. These results may imply that the mutations in the VP1 coding region contribute to attenuation.
TL;DR: The DNA sequence of a cloned cDNA that is complementary to the mRNA for the 50 kilodalton (kd) human epidermal keratin is determined, providing the first amino acid sequence for a cytoskeletal keratin.
TL;DR: Evidence that two species of HPRT mRNA, which differ in the site of polyadenylation that is utilized during processing of the RNA transcripts, exist in Chinese hamster cells is presented.
Abstract: Recombinant plasmids containing DNA inserts complementary to mRNA coding for hypoxanthine-guanine phosphoribosyltransferase (HPRT) from mouse and Chinese hamster cell lines have been isolated from cDNA libraries and characterized by DNA sequence analysis. A total of 1292 nucleotides of the mouse cDNA sequence and 1301 nucleotides of the Chinese hamster cDNA sequence has been determined. Each of these sequences includes an open reading frame of 654 nucleotides (218 amino acids) corresponding to the HPRT protein coding region. The deduced amino acid sequences for the mouse and Chinese hamster enzymes are presented and compared to that of human HPRT. At least 95% of the amino acids are conserved in the three species. In addition, we present evidence that two species of HPRT mRNA, which differ in the site of polyadenylation that is utilized during processing of the RNA transcripts, exist in Chinese hamster cells.
TL;DR: A cDNA clone of the mRNA encoding the glycoprotein (G) of vesicular stomatitis virus was inserted into plasmid vectors under the control of either the SV40 early promoter (pSV2G) or the SV 40 late promoter ( pSVGL).
TL;DR: A comparison of the amino acid sequences of human and anglerfish preprosom atostatin I indicated that the COOH-terminal region encoding somatostatin-14 and the adjacent 6 amino acids are highly conserved, whereas the remainder of the molecule, including the signal peptide region, is more divergent.
Abstract: RNA has been isolated from a human pancreatic somatostatinoma and used to prepare a cDNA library. After prescreening, clones containing somatostatin I sequences were identified by hybridization with an anglerfish somatostatin I-cloned cDNA probe. From the nucleotide sequence of two of these clones, we have deduced an essentially full-length mRNA sequence, including the preprosomatostatin coding region, 105 nucleotides from the 5' untranslated region and the complete 150-nucleotide 3' untranslated region. The coding region predicts a 116-amino acid precursor protein (Mr, 12.727) that contains somatostatin-14 and -28 at its COOH terminus. The predicted amino acid sequence of human somatostatin-28 is identical to that of somatostatin-28 isolated from the porcine and ovine species. A comparison of the amino acid sequences of human and anglerfish preprosomatostatin I indicated that the COOH-terminal region encoding somatostatin-14 and the adjacent 6 amino acids are highly conserved, whereas the remainder of the molecule, including the signal peptide region, is more divergent. However, many of the amino acid differences found in the pro region of the human and anglerfish proteins are conservative changes. This suggests that the propeptides have a similar secondary structure, which in turn may imply a biological function for this region of the molecule.
TL;DR: Four cDNA clones containing cardiac myosin heavy chain (MHC) inserts have been characterized and nucleotide and amino acid sequences reveal a highly conserved structure in the light meromyosin portion of MHC from striated muscle tissues.
Abstract: Four cDNA clones containing cardiac myosin heavy chain (MHC) inserts have been characterized. Hybridization and nucleotide sequence analysis identify two different MHC genes coding for proteins of different length that are both specifically expressed in the adult heart. The nucleotide and amino acid sequences reveal a highly conserved structure in the light meromyosin portion of MHC from striated muscle tissues.
TL;DR: A gene encoding one of the 19,000 dalton zein proteins from a maize genomic library constructed in Charon 4A is isolated, and a basis for microheterogeneity within the gene family is identified.
TL;DR: The structural gene of the sweet-tasting plant protein (prepro)thaumatin was cloned and expressed in Escherichia coli and expression was effected under control of lac and trp promoter/operator systems and through the use of bacterial ribosome-binding sites.
TL;DR: A recombinant plasmid containing human immune interferon (IFN-gamma) cDNA was identified by hybridization ofplasmid inserted DNA bound onto nitrocellulose filters with mRNA derived from SEA-induced splenocytes, translation of the eluted RNA in Xenopus laevis oocytes and assaying for IFN activity.
Abstract: Starting with mRNA derived from Staphylococcal enterotoxin A induced human splenocytes, dsDNA was synthesized and inserted into unique BamHI site of the eukaryotic expression vector pSV529 (1). A recombinant plasmid containing human immune interferon (IFN-gamma) cDNA was identified by hybridization of plasmid inserted DNA bound onto nitrocellulose filters with mRNA derived from SEA-induced splenocytes, translation of the eluted RNA in Xenopus laevis oocytes and assaying for IFN activity. Plasmids containing the entire human IFN-gamma cDNA sequence were identified by colony hybridization and were sequenced. A unique coding region was identified which predicted a protein of 166 amino acids, the 20 N-terminal amino acids of which presumably represent a signal peptide. After transfection of monkey cells with plasmid DNA isolated from one of the recombinant clones (pHIIF-SV-gamma 1), IFN was excreted into the culture medium. This IFN was not distinguishable from human IFN-gamma by serological criteria or by cell target species specificity.
TL;DR: It is suggested that ATLV should be classified in a distinct group of retroviruses with bovine leukemia virus which also makes unusually long strong-stop cDNA.
Abstract: Adult T-cell leukemia virus (ATLV) is a human retrovirus closely associated with adult T-cell leukemia. The integrated provirus DNA and cDNA from virion RNA were molecularly cloned and their structures were analyzed. Clone lambda ATM-1 of an integrated provirus DNA in the MT-1 cell line, established from adult T-cell leukemia cells by cocultivation with cord lymphocytes, contained DNA about 13,000 base pairs (bp) long and long terminal repeats (LTR) at both ends of the viral sequence that were about 8,000 bp long. These two LTR sequences were linked to cellular sequences with direct repeats of 7 bp. Each LTR consisted of 754 bp including inverted repeats of 2 bp at the ends and the T-A-T-A-A box, characteristics in common with those of LTRs of other known retroviruses. Adjacent to the 5' LTR there was a sequence identical to the tRNAPro binding site in murine leukemia virus, suggesting that tRNAPro is a primer for reverse transcription of the viral genome. From these structural features, the mechanism of ATLV replication was suggested to be the same as that of other known animal retroviruses. However, the length of the small terminal repeats at the ends of the RNA genome, 228 +/- 1 bases, is much longer than the lengths, up to 80 bases, of those in avian, mouse, or primate retroviruses so far analyzed. These findings suggest that ATLV should be classified in a distinct group of retroviruses with bovine leukemia virus which also makes unusually long strong-stop cDNA.
TL;DR: Introduction of a segment containing the SV40 early polyadenylation signal into the 3' end of the DH FR cDNA gene generated a recombinant capable of transforming cells to the DHFR+ phenotype with at least a 10-fold increase in efficiency, demonstrating the necessity for an efficient polyadenyation signal.
Abstract: Dihydrofolate reductase (DHFR) modular genes have been constructed with segments containing the adenovirus major late promoter, a 3' splice site from a variable region immunoglobulin gene, a DHFR cDNA, and portions of the simian virus 40 (SV40) genome. DNA-mediated transfer of these genes transformed Chinese hamster ovary DHFR- cells to the DHFR+ phenotype. Transformants contained one to several copies of the transfected DNA integrated into the host genome. Clones subjected to growth in increasing concentrations of methotrexate eventually gave rise to lines containing several hundred copies of the transforming DNA. Analysis of the DHFR mRNA produced in amplified lines indicated the following. (i) All clones utilize the adenovirus major late promoter for transcription initiation. (ii) A hybrid intron formed by the 5' splice site of the adenovirus major late leader and a 3' splice site from a variable-region immunoglobulin gene is properly excised. (iii) The mRNA is not efficiently polyadenylated at sequences in the 3' end of the DHFR cDNA but rather uses polyadenylation signals downstream from the DHFR cDNA. Three independent clones produce a DHFR mRNA containing SV40 or pBR322 and SV40 sequences, and the RNA is polyadenylated at the SV40 late polyadenylation site. Another clone has recombined into cellular DNA and apparently uses a cellular sequence for polyadenylation. Introduction of a segment containing the SV40 early polyadenylation signal into the 3' end of the DHFR cDNA gene generated a recombinant capable of transforming cells to the DHFR+ phenotype with at least a 10-fold increase in efficiency, demonstrating the necessity for an efficient polyadenylation signal. Attachment of a DNA segment containing the transcription enhancer (72-base pair repeat) of SV40 further increased the biological activity of the modular DHFR gene 50- to 100-fold.
TL;DR: cDNA clones corresponding to a major histocompatibility class III antigen, the complement protein factor B, have been isolated from a human adult liver cDNA library and the sequences of two clones have been partially determined.
Abstract: cDNA clones corresponding to a major histocompatibility class III antigen, the complement protein factor B, have been isolated from a human adult liver cDNA library. The clones, ranging in size from 1.0 to 2.3 kilobases, were identified by direct hybridization with two synthetic oligonucleotide mixtures. Two regions of the factor B amino acid sequence, each with minimal ambiguity in codon assignment, were chosen for synthesis of the oligonucleotides. The sequences of two clones have been partially determined. They contain coding information for the amino acid sequence of the Bb fragment of factor B and the entire 3' -untranslated region.
TL;DR: Recombinant plasmids containing cDNA inserts from human leukocyte interferon (IFN-alpha), fibroblast interferons (ifN-beta), or immune interferON (INF-gamma) genes were radiolabeled and hybridized in situ to human metaphase chromosome preparations.
Abstract: Recombinant plasmids containing cDNA inserts from human leukocyte interferon (IFN-α), fibroblast interferon (IFN-β), or immune interferon (INF-γ) genes were radiolabeled and hybridized in situ to human metaphase chromosome preparations. The results localized the human IFN-α and IFN-β genes to the short arm of chromosome 9(p21→pter) and localized the IFN-γ gene to the long arm of chromosome 12(q24.1).
TL;DR: The usefulness of the cytoplasmic inhibitor of RNase to protect RNA in the course of the synthesis of complementary DNA by reverse transcriptase is discussed.
Abstract: Publisher Summary Bovine Ribonuclease has been a test protein in the study of a wide variety of chemical and physical methods of protein chemistry. It is widely employed in the course of the sequencing of RNA. This chapter discusses the usefulness of the cytoplasmic inhibitor of RNase to protect RNA in the course of the synthesis of complementary DNA by reverse transcriptase. It examines the use of the inhibitor to protect mRNA during the course of in vitro translation and during the preparation of rough microsomes and detached polysomes. The introduction of affinity chromatography has simplified the isolation of pure RNases by providing a highly efficient method for separating active enzymes from molecules that do not have an affinity for the coupled substrate analog. The technique can be used as an early step in purification or as a final step after ion exchange chromatography and gel filtration to isolate an RNase fraction of given charge and size.
TL;DR: The presence of glycine and a pair of basic amino acid residues adjacent in the carboxyl-terminal phenylalanine of gastrin indicates that the glycine may be required for the enzymatic amidation of phenyl Alanine to phenylAlanine amide.
Abstract: We have cloned in EScherichia coli a cDNA copy of mRNA coding for the porcine antral mucosal hormone preprogastrin. Full-length double-stranded cDNA was synthesized and inserted into the Pst I endonuclease site in plasmid pBR322 by using a homopolymeric extension technique. A partial cDNA clone was used as a probe to identify a complete cDNA clone in a cDNA library by colony hybridization. Four positive clones were isolated, one of which corresponded to porcine preprogastrin mRNA. The nucleotide sequence of the cDNA insert (602 nucleotides) revealed 312 nucleotides in the entire mRNA coding region, 61 nucleotides in the 5' untranslated region, 86 nucleotides in the 3'untranslated region, and a poly(A) tail of 86 nucleotides. Gastrin is located near the carboxyl end of preprogastrin and is flanked at both its amino and carboxyl ends by a pair of basic amino acid residues. The presence of glycine and a pair of basic amino acid residues adjacent in the carboxyl-terminal phenylalanine of gastrin indicates that the glycine and a pair of basic amino acid residues may be required for the enzymatic amidation of phenylalanine to phenylalanine amide.
TL;DR: The proteolipid subunit of the mitochondrial ATP synthase from Neurospora crassa is an extremely hydrophobic protein of 81 amino acid residues, which is imported into mitochondria as a precursor of mol.
Abstract: The proteolipid subunit of the mitochondrial ATP synthase from Neurospora crassa is an extremely hydrophobic protein of 81 amino acid residues, which is imported into mitochondria as a precursor of mol. wt. 15 000. The primary structure of the imported form has now been determined by isolating and analyzing cDNA clones of the preproteolipid mRNA. An initial cDNA clone was identified by hybridizing total polyadenylated RNA to pooled cDNA recombinant plasmids from an ordered clone bank and subsequent cell-free translation of hybridization-selected mRNA. Further preproteolipid clones were identified at a frequency of 0.2% by colony filter hybridization. One isolated cDNA represented the major part of the preproteolipid mRNA. The nucleotide sequence showed 243 bases corresponding to the mature proteolipid and, in addition, 178 bases coding for an amino-terminal presequence . Non-coding sequences of 48 bases at the 5' end and of 358 bases at the 3' end plus a poly(A) tail were determined. The long presequence of 66 amino acids is very polar, in contrast to the lipophilic mature proteolipid, and includes 12 basic and no acidic side chains. It is suggested that the presequence is specifically designed to solubilize the proteolipid for post-translational import into the mitochondria.