1. The size of nascent globin peptides from which the N-terminal methionine residue is cleaved has been investigated by comparing the proportion of N-terminal methionine and valine in short and long chains. Nascent chains were labelled in rabbit reticulocyte lysates, fractionated according to length by chromatography on Sephadex G-50, and analysed by the Edman degradation of selected pooled fractions. It was found that different peptide fractions contained either methionine or valine, but not both, as the N-terminal residue. Methionine was present at the N-terminus of globin chains containing up to approx. 50 amino acids whereas valine was found to be the N-terminal amino acid of longer peptides. 2. In similar experiments with nascent proteins of rat liver, labelled either in vivo or in a cell-free system containing microsomal material and cell sap, evidence was obtained for the presence of methionine at the N-terminus of nascent chains up to approx. 65 amino acid residues long. Thus protein synthesis in liver appears to be initiated also by methionine, but in this case cleavage takes place somewhat later during peptide elongation than in globin synthesis.
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Research Article|
August 01 1973
The presence of N-terminal methionine on nascent protein of rat liver and rabbit reticulocytes and its cleavage during polypeptide-chain elongation
Anna Koffer-Gutmann;
Anna Koffer-Gutmann
1Department of Biochemistry, University of London King's College, Strand, London WC2R 2LS, U.K.
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Henry R. V. Arnstein
Henry R. V. Arnstein
1Department of Biochemistry, University of London King's College, Strand, London WC2R 2LS, U.K.
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Publisher: Portland Press Ltd
© 1973 London: The Biochemical Society
1973
Biochem J (1973) 134 (4): 969–983.
Citation
Anna Koffer-Gutmann, Henry R. V. Arnstein; The presence of N-terminal methionine on nascent protein of rat liver and rabbit reticulocytes and its cleavage during polypeptide-chain elongation. Biochem J 1 August 1973; 134 (4): 969–983. doi: https://doi.org/10.1042/bj1340969
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