Showing papers on "Homology (biology) published in 1982"

Four small Drosophila heat shock proteins are related to each other and to mammalian alpha-crystallin

Abstract: The primary base sequence of the protein coding regions of the four small heat shock genes of Drosophila melanogaster present at cytological locus 67B has been determined. A single open reading frame large enough to encode a small heat shock protein is found for each gene. The molecular weights of the predicted proteins are in good agreement with experimentally determined values obtained from gel electrophoresis. The predicted amino acid sequences of the four small heat shock genes show striking homologies over approximately 50% of their lengths. This region of extensive homology extends from about amino acid 85 to amino acid 195 out of a total of approximately 200 amino acids. Comparison of the predicted sequence with the known sequences of other proteins revealed a remarkable similarity between this region of homology and the corresponding region of mammalian alpha-crystallin. The possible functional significance of this structural similarity is discussed.

Neuronal cell Thy-1 glycoprotein: homology with immunoglobulin

Abstract: The amino acid sequences of mouse brain Thy-1 glycoproteins are shown to be homologous to those of variable-region immunoglobulin domains. There is also good homology with constant domains and beta 2-microglobulin; overall the results suggest that Thy-1 may be like the primordial immunoglobulin domain. Preliminary evidence for an invertebrate Thy-1 homolog supports this possibility.

Human metallothionein genes--primary structure of the metallothionein-II gene and a related processed gene.

Abstract: The complete nucleotide sequence of two of the human metallothionein gene family has been compared. One is a functional metallothionein-II gene, the other a pseudogene, lacking introns, terminating in a poly(A) tail and flanked by two direct repeats. In addition, we have detected a size polymorphism associated with the processed gene in the population, examined, and we have observed a region of apparent secondary structure homology between of 5' flanking region of the functional metallothionein-II gene and that of a mouse metallothionein-I gene.

Homology among DNA-binding proteins suggests use of a conserved super-secondary structure.

Abstract: The amino acid sequences of the repressor and cro proteins of phages lambda, 434 and P22 are homologous, especially in a region in which repressor and lambda cro have a similar alpha-helix-turn-alpha-helix secondary structure Model-building studies indicate that this structure is important in DNA binding, and we suggest it may be a common feature of many DNa-binding proteins

Isolation and structural organization of the human preproenkephalin gene

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.

The nucleotide sequence of a human immunoglobulin C gamma1 gene.

Abstract: We report the nucleotide sequence of a gene encoding the constant region of a human immunoglobulin gamma 1 heavy chain (C gamma 1). A comparison of this sequence with those of the C gamma 2 and C gamma 4 genes reveals that these three human C gamma genes share considerable homology in both coding and noncoding regions. The nucleotide sequence differences indicate that these genes diverged from one another approximately 608 million years ago. An examination of hinge exons shows that these coding regions have evolved more rapidly than any other areas of the C gamma genes in terms of both base substitution and deletion/insertion events. Coding sequence diversity also is observed in areas of CH domains which border the hinge.

Avian sarcoma virus Y73 genome sequence and structural similarity of its transforming gene product to that of Rous sarcoma virus

Abstract: From the complete nucleotide sequence of the genome of the avian sarcoma virus Y73, we have predicted amino acid sequence of p90gag-yes, the product of the transforming gene. Contrary to previous evidence from molecular hybridization studies, p90gag-yes was found to have much homology with the transforming gene product p60src of Rous sarcoma virus, suggesting that the cellular counterparts of the two (c-yes and c-src) originated from a common prototype sequence.

Structures of the genes for the β and ε subunits of spinach chloroplast ATPase indicate a dicistronic mRNA and an overlapping translation stop/start signal

Abstract: A 2,4-kilobase-pair region of spinach chloroplast DNA adjacent to the gene for the large subunit of ribulosebisphosphate carboxylase has been analyzed by RNA hybridization, in vitro transcription/translation, and DNA sequence determination. The analysis indicates that this region carries the genes for the β and e subunits of chloroplast ATPase and that the two genes are cotranscribed into a dicistronic mRNA with 4-base-pair overlap between the stop codon of the β-subunit gene and the start codon of the e-subunit gene. The ATPase and carboxylase genes are transcribed divergently with respect to each other. The deduced amino acid sequences of the β and e subunits from spinach show 67% and 26% homology, respectively, with the published sequences of the β and e subunits of Escherichia coli ATPase.

Nucleotide Sequence and Secondary Structure of Citrus Exocortis and Chrysanthemum Stunt Viroid

Abstract: The complete nucleotide sequence of citrus exocortis viroid (CEV, propagated in Gymura) and chrysanthemum stunt viroid (CSV, propagated in Cineraria) has been established, using labelling in vitro and direct RNA sequencing methods and a new screening procedure for the rapid selection of suitable RNA fragments from limited digests. The covalently closed circular single-stranded viroid RNAs consist of 371 (CEV) and 354 (CSV) nucleotides, respectively. As previously shown for potato spindle tuber viroid (PSTV, 359 nucleotides), CEV and CSV also contain a long polypurine sequence. Maximal base-pairing of the established CEV and CSV sequences results in an extended rod-like secondary structure similar to that previously established for PSTV and as predicted from detailed physicochemical studies of all these viroids. Although the three viroid species sequenced to date differ in size and nucleotide sequence, there is 60--73% homology between them. As PSTV, CEV and CSV also contain conserved complementary sequences which are separated from each other in the native secondary structure. We postulate that the resulting 'secondary' hairpins, being formed and observed in vitro during the complex process of thermal denaturation of viroid RNA, must have a vital, although yet unknown, function in vivo. The possible origin and function of viroids are discussed on the basis of the characteristic structural features and of a considerable homology with U1a RNA found for a region highly conserved in the three viroids.

Structure and expression of a mouse major histocompatibility antigen gene, H-2Ld

Abstract: A genomic clone encoding H-2Ld, a mouse major transplantation antigen, has been identified and the structure of the H-2Ld gene has been partially determined. We isolated 35 genomic clones from a BALB/c (H-2d) genomic library by hybridization to mouse or human probes. One of these clones encodes H-2Ld as determined by two criteria. First, the gene encodes a protein that is identical at the 76 known amino acid positions for H-2Ld. Second, when introduced into L cells by DNA-mediated gene transfer, a new H-2 antigen is expressed that is recognized by anti-H-2Ld monoclonal antibodies. The sequence of the H-2Ld protein predicted by the DNA sequences shows more than 80% homology to known H-2 antigens. H-2L-like sequences are found in mutant H-2Kb molecules, suggesting that gene conversion or reciprocal recombination may play a role in the development of H-2 polymorphism.

Linkage and sequence homology of two human immunoglobulin gamma heavy chain constant region genes

Abstract: We report the nucleotide sequence of a gene encoding a human immunoglobulin C gamma 2 region. Comparison with the previously determined C gamma 4 sequence reveals that these two genes share extensive (approximately 95%) homology in the three CH domain exons and adjacent noncoding regions. In contrast, hinge exons have diverged to a much greater degree, implying that natural selection has favored the generation of diversity in these coding regions. We have used the noncoding nucleotide differences to estimate that approximately 6-7 million years have elapsed since the occurrence of the gene duplication or correction event which generated the two identical ancestral genes. In addition we show that the two C gamma genes are arranged in human chromosomal DNA in the configuration 5'-C gamma 2-17 kilobase pairs -C gamma 4-3'.

Direct evidence of homology between human DC-1 antigen and murine I-A molecules.

Abstract: The nature of the interactions between cells of the immune system has been shown to be directly related to a group of antigens present on the surface of B lymphocytes. These antigens are under genetic control of the HLA-D/DR region of the human major histocompatibility complex (MHC) located on chromosome 6. DR antigens (the products of the HLA-DR locus within this region), have been defined by serological studies. Recently another antigen, DC-1, has been serologically defined. In the mouse, the I region, analogous to the HLA-D/DR region in man, has been subdivided into at least five subregions (A, B, J, E and C) and specific functions and cell populations associated with each of the subregions. Although in man the HLA-D/DR region cannot at present be subdivided, limited NH2-terminal amino acid sequence data have shown that the DR molecule is homologous to the I-E molecule of the mouse. Furthermore, evidence that DC-1 is not homologous to I-E (and might therefore be homologous to I-A) has been reported. We now report that, using immunoadsorbents prepared with monoclonal antibodies specific for DR or DC-1 antigens, these two human alloantigens were purified from a human lymphoblastoid cell line (LB) and the chains were separated. The NH2-terminal amino acid sequence of the heavy chain of DC-1 antigen shows great structural homology with the murine I-A molecules, thus providing direct evidence of homology of DC-1 to murine I-A.

Soybean leghemoglobin gene family: normal, pseudo, and truncated genes

Abstract: Leghemoglobin (Lb) genes in soybean represent a small family of closely related genes. Three Lb sequences isolated from a genomic library were analyzed at the nucleotide sequence level. A Lb gene present on an 11.5-kilobase (kb) EcoRI genomic fragment spans approximately 1,200 nucleotides and is interrupted at amino acid positions 32 to 33, 68 to 69, and 103 to 104. The intervening sequences, as well as the 5' and 3' flanking regions of this gene, contain the consensus sequences found in other eukaryotic genes. The length of the 5'-untranslated region is 49 bases as determined by nuclease S1 mapping. R-loop analysis of the DNA from the recombinant phage containing the 11.5-kb EcoRI genomic fragment showed that another Lb gene is located 2.5 kb away. The nucleotide sequence of the second gene showed that this gene is incomplete, containing only exons 3 and 4. The deduced amino acid sequence of this gene, although showing 76% homology with the corresponding region of the other Lb gene, is not represented in any of the known Lb proteins. Both genes are oriented in the same direction with respect to the coding strand. Analysis of the sequence present on a second genomic clone containing a 4.2-kb EcoRI fragment revealed a truncated Lb gene showing homology with the last exon and the noncoding region at the 3' end of the two other Lb genes.

Conserved Regions of Homologous G-Banded Chromosomes Between Orders in Mammalian Evolution: Carnivores and Primates

Abstract: The recent derivation of a biochemical map of 33 loci of the domestic cat (Felis catus) revealed a striking conservation of chromosomal linkage associations between the cat and humans. A comparison of homologous (by linkage criteria) chromosomes by using conventionally extended and high-resolution G-banding of human and feline chromosomes is presented. Four criteria for establishing probable cytogenetic homologies of chromosomal regions were invoked: (i) map placement of homologous genes to the same chromosomes; (ii) cytological correlation of G-banding pattern; (iii) placement of homologous genes, by regional gene mapping, in the region of cytological homology; and (iv) a requirement that the putative region of homology be ancestral and evolutionarily conserved within their respective orders. Five subchromosomal regions (homologous to human chromosome 1p, 2p, 2q, 12, and X) were found to be conserved and homologous by all the stated criteria. The conserved regions constitute nearly 20% by length of the human chromosomal genome. The implications of conservation of chromosome homologies between mammalian orders whose last common ancestor became extinct more than 60 million years ago is discussed.

Independently evolving chicken histone H2B genes: identification of a ubiquitous H2B-specific 5′ element

Abstract: The DNA sequence of two chicken histone H2B genes has been determined. Both genes code for the same H2B subtype. Except for conserved "promoter" elements, the sequences 5' to the protein coding regions are completely divergent, indicating that the genes are distantly related and are not evolving in concert. This presents an ideal situation for sequence comparisons. We have discovered a 13 bp, H2B specific homology block, 5' CTCATTTGCATAC 3' located close to the "TATA box". This motif is conserved in all H2B gene leader regions so far sequenced. One of the H2B genes is closely linked, in a divergent arrangement, to an H2A gene, and sequence data suggests that the linked genes share promoter elements.

Comparison of nucleotide sequences of mRNAs belonging to the mouse H-2 multigene family

Abstract: The complete nucleotide sequences of three cDNAs coding for the C-terminal part of mouse histocompatibility (H-2) antigens, and for the 3' non coding regions of these clones have been determined. Comparison of the sequence indicates a large homology throughout the coding and non-coding regions and suggests the existence of a genetic mechanism which homogenizes nucleotide sequences among genes of the H-2 multigene family.

Two yeast acid phosphatase structural genes are the result of a tandem duplication and show different degrees of homology in their promoter and coding sequences.

Abstract: We have cloned the structural genes for a regulated ( PHO5 ) and a constitutive ( PHO3 ) acid phosphatase from yeast by transformation and complementation of a yeast pho3 , pho5 double mutant. Both genes are located on a 5.1-kb BamHI fragment. The cloned genes were identified on the basis of genetic evidence and by hybrid selection of mRNA coupled with in vitro translation and immunoprecipitation. Subcloning of partial Sau3A digests and functional in vivo analysis by transformation together with DNA sequence analysis showed that the two genes are oriented in the order (5') PHO5 , PHO3 (3'). While the nucleotide sequences of the two coding regions are quite similar, the putative promoter regions show a lower degree of sequence homology. Partly divergent promoter sequences may explain the different regulation of the two genes.

A Gene Deletion is Responsible for Absence of Human Chorionic Somatomammotropin

Abstract: We have examined the human growth hormone (hGH) and human chorionic somatomammotropin (hCS) family of genes in genomic DNA from an individual with complete antenatal deficiency of hCS. Following digestion with a variety of bacterial restriction endonucleases, the DNA from this individual produced fewer fragments with homology to a radiolabeled hCS cDNA probe than did control DNA specimens. The patterns indicated that his DNA contained the normal hGH gene and an "hGH-like" gene, but lacked the hCS gene, a variant hGH gene, and another gene or genes with structural homology to hGH and hCS, which were present in all control DNA specimens. The findings were consistent with homozygosity for a gene deletion with a minimum length of 18.5 kb. Analysis of polymorphic restriction site variation related to the hGH and hCS gene cluster indicated that both parents and three older siblings were heterozygous for the deletion. The association between gene deletion and a normal growth pattern in this individual indicates ...

Structural homologies among type I restriction-modification systems.

Abstract: Structural homologies among different restriction systems of Escherichia coli and several Salmonella species have been investigated by immunological methods using antibodies prepared against two subunits of the E. coli K12 restriction enzyme, and by DNA hybridization experiments using different fragments of the E. coli K12 hsd genes as probes. The results with both techniques show a strong homology between the E. coli K12 and B restriction-modification systems, weaker but nevertheless marked homology between E. coli K12 and the Salmonella systems SB, SP, and SQ and, surprisingly, no homology between the E. coli K12 and A systems.

Structural alterations in J regions of mouse immunoglobulin λ genes are associated with differential gene expression

Abstract: Immunoglobulin λ light chains in the mouse comprise three types: λ1, λ2 and λ3 (refs 1–3 respectively) and are encoded by three constant region (Cλ) and two variable region (Vλ) genes. The Cλ2 and Cλ3 protein sequences differ at only 5 amino acid positions whereas Cλ1 differs from both by about 30 amino acids. The Cλ1 and Cλ3 genes are closely linked4, separated by ∼3 kilobases (kb) of DNA. The Cλ2 gene is closely linked to a Cλ4 gene, but is an unknown distance from the Cλ3–Cλ1 cluster4,5. Although the Cλ4 gene shares homology with Cλ1, we show here that it represents a pseudogene. Only two germ-line V genes appear to be expressed in mouse λ chains: Vλ1 is used in association with either Cλ1 (ref. 1) or Cλ3 (ref. 6), while Vλ2 has only been found with Cλ2 (ref. 2). Differential gene expression is observed in the λ locus. Among mouse serum antibodies, λ1 chains occur 10 times more frequently than λ2 (ref. 7) or λ3 (ref. 3) chains while λ4 chains have not been identified. We have now searched for structural differences between Cλ genes which could explain this differential expression. Our nucleotide sequence analysis indicates that Cλ4 is not expressed due to an inactive RNA splice site. Although no structural defects were found in Cλ2 or Cλ3, substitutions in the rearrangement recognition sequences associated with Jλ2 and Jλ3 segments, together with nearby competing pseudo recognition sequences, may explain the relatively low levels of Cλ2 and Cλ3 gene expression.