Signal sequences: The limits of variation

The focusing positions in narrow range immobilized pH gradients of 29 polypeptides of known amino acid sequence were determined under denaturing conditions. The isoelectric points of the proteins calculated from their amino acid sequences matched with good accuracy the experimentally determined pI values. We show the advantages of being able to predict the position of a protein of known structure within a two-dimensional gel.

The focusing positions of polypeptides in immobilized pH gradients can be predicted from their amino acid sequences

The molecular mechanisms of the metabolism and transport of iron in normal and neoplastic cells.

Molecular analysis of the human trk oncogene, a transforming gene isolated from a colon carcinoma biopsy, revealed the existence of a novel member of the tyrosine kinase gene family. This locus, which we now designate the trk proto-oncogene, codes for a protein of 790 amino acid residues that has several features characteristic of cell surface receptors. They include (i) a 32-amino-acid-long putative signal peptide, (ii) an amino-terminal moiety (residues 33 to 407) rich in consensus sites for N-glycosylation, (iii) a transmembrane domain, (iv) a kinase catalytic region highly related to that of other tyrosine kinases, and (v) a very short (15 residue) carboxy-terminal tail. Residues 1 to 392 were absent in the trk oncogene, as they were replaced by tropomyosin sequences. However, no other differences were found between the transforming and nontransforming trk alleles (residues 392 to 790), suggesting that no additional mutations are required to activate the transforming potential of this gene. The human trk proto-oncogene codes for a 140,000-dalton glycoprotein, designated gp140proto-trk. However, its primary translational product is a 110,000-dalton glycoprotein which becomes immediately glycosylated, presumably during its translocation into the endoplasmic reticulum. This molecule, designated gp110proto-trk, is further glycosylated to yield the mature form, gp140proto-trk. Both gp110proto-trk and gp140proto-trk proteins possess in vitro kinase activity specific for tyrosine residues. Finally, iodination of intact NIH 3T3 cells expressing trk proto-oncogene products indicated that only the mature form, gp140proto-trk, cross the plasma membrane, becoming exposed to the outside of the cell. These results indicate that the product of the human trk locus is a novel tyrosine kinase cell surface receptor for an as yet unknown ligand.

Molecular and biochemical characterization of the human trk proto-oncogene.

IRON IN BIOORGANIC EVOLUTION. An Introduction to the Nature of Iron Transport and Storage. Iron-Dependent Enzymes in Mammalian Systems. Parallels in the Mode of Regulation of Iron Assimilation in All Living Species. Iron and Oxygen: A Dangerous Mixture. STRUCTURE OF PROTEINS OF IRON STORAGE AND TRANSPORT. Transferrin and Lactoferrin. Ferritin. MOLECULAR BIOLOGY OF PROTEINS OF IRON TRANSPORT AND STORAGE. Molecular Biology of the Transferrins. Molecular Analysis of the Transferrin Receptor and Its Gene. Ferritin Gene Structure and Expression. ROLE OF IRON AND PROTEINS OF IRON METABOLISM IN CELL PROLIFERATION AND MALIGNANCY. Iron-Transferrin Requirements and Transferrin Receptor Expression in Proliferating Cells. Ribonucleotide Reductase. Ferritin in Malignant Cells. IRON METABOLISM IN SPECIFIC TISSUES. Comparative Aspects of Iron Transport and Storage in Different Tissues. Developmental Changes in Iron Storage (the Ferritins) and Iron Transport (the Transferrins and Transferrin Receptors). Intestinal Iron Metabolism and Absorption. Erythroid Cell Iron Metabolism and Heme Synthesis. Iron Metabolism in the Reticuloendothelial System. Modulation of the Availability of Intracellular Iron. Iron and Proteins of Iron Metabolism in the Central Nervous System.

https://febs.onlinelibrary.wiley.com/doi/pdf/10.1111/j.1432-1033.1987.tb11155.x

Iron Transport and Storage

Human genomic clones of the haptoglobin Hp1F and the "haptoglobin related' gene (Hpr) have been isolated. The two genes are adjacent, spanning a region of approximately 21 kb. A comparison of their coding sequences shows that Hpr differs from Hp1F at 28 codons. Northern blot and primer elongation analyses with human liver RNA show that the haptoglobin gene Hp1F appears to be transcribed some 1000-fold less in fetal than in adult liver. In adult liver the amount of Hpr mRNA is at the lower limit of detection, therefore the extent of its expression is at most less than 1000-fold that of the Hp1F gene. No Hpr mRNA can be detected in fetal liver.

Structure and expression of the human haptoglobin locus.

We have isolated and sequenced a cDNA clone coding for human Retinol Binding Protein. The sequence indicates that Retinol Binding Protein is synthesized as a single polypeptide chain precursor which is then matured to the secreted protein by removal of a leader peptide. Southern and Northern blot analysis suggest that the gene is present in one or few copies per haploid genome and is transcribed in a single mRNA species.

Cloning and sequencing of a full length cDNA coding for human retinol-binding protein

We have cloned a segment of cDNA from human liver coding for an apoferritin subunit, probably an H chain. Sequence comparison with the available protein sequence shows that our clone corresponds to a ferritin subunit present as a minor species in human spleen and placenta, but as major species in HeLa cells. Northern blot analysis shows the existence of only one band of similar size in human liver, HeLa cells, Daudi lymphoma and Hep3B hepatoma cell lines. In contrast, Southern blot analysis provides evidence for a multigene family.

Cloning and sequencing of a full length cDNA coding for a human apoferritin H chain: evidence for a multigene family.

We have isolated and sequenced a cDNA clone coding for human haptoglobin. Our sequence shows that haptoglobin is very likely synthesized as a single polypeptide chain which is then cleaved at an Arg residue to generate its two characteristic alpha and beta subunit. Southern blot analysis suggests that there are at least two copies of the haptoglobin gene per haploid genome.

G. Bensi

Papers

Structure and expression of the human haptoglobin locus.

Cloning and sequencing of a full length cDNA coding for human retinol-binding protein

Cloning and sequencing of a full length cDNA coding for a human apoferritin H chain: evidence for a multigene family.

Sequence of human haptoglobin cDNA: evidence that the alpha and beta subunits are coded by the same mRNA.