Synthesis and degradation of termination and premature-termination fragments of beta-galactosidase in vitro and in vivo

Manley, J. L. (November 1978) Synthesis and degradation of termination and premature-termination fragments of beta-galactosidase in vitro and in vivo. J Mol Biol, 125 (4). pp. 407-32. ISSN 0022-2836 (Print)0022-2836 (Linking)

URL: http://www.ncbi.nlm.nih.gov/pubmed/105143
DOI: 10.1016/0022-2836(78)90308-X

Abstract

A number of abnormal polypeptides which are products of the lacZ gene in Escherichia coli have been characterized. A variety of experiments indicates that one class of at least nine different fragments arises from premature termination of protein synthesis. They have been detected as products of protein synthesis both in vitro and in vivo, although the percentage of fragments made in vitro is greater than that in vivo. The percentage of total Z gene-encoded protein which is found as fragments is estimated to be roughly 23% in vivo. This means that about 31% of the total number of β-galactosidase monomers synthesized are prematurely terminated molecules. The average molecular weight of the polypeptides produced is 91,000. This corresponds to a termination event occurring on the average once every 3200 codons. The sites at which termination occurs appear to be specific and are located primarily near the 3′-end of the gene. Polypeptides synthesized in vitro and in vivo from templates containing mutations in the Z gene have also been compared. Most of the mutationally generated fragments synthesized in vitro are stable, unlike their in vivo counterparts, which are often rapidly degraded. One fragment, however, generated by an early amber mutation in the Z gene, is degraded in the in vitro system. The mechanism of degradation appears to be specific for small abnormal polypeptides. Internal reinitiation polypeptides generated by nonsense mutations, which have been found in vivo, are not detected in the in vitro protein synthesis system under the conditions used here.

Item Type: Paper
Uncontrolled Keywords: Amino Acid Sequence Escherichia coli/genetics/metabolism Galactosidases/*biosynthesis Lac Operon Molecular Weight Mutation *Peptide Chain Termination, Translational Peptide Fragments/*biosynthesis Suppression, Genetic beta-Galactosidase/*biosynthesis
Subjects: bioinformatics > genomics and proteomics > genetics & nucleic acid processing > protein structure, function, modification
bioinformatics > genomics and proteomics > genetics & nucleic acid processing > protein structure, function, modification > protein types > N-terminal acetylation
CSHL Authors:
Communities: CSHL labs
Depositing User: Matt Covey
Date: 15 November 1978
Date Deposited: 14 Dec 2016 17:10
Last Modified: 14 Dec 2016 17:10
Related URLs:
URI: http://repository.cshl.edu/id/eprint/33288

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