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Stimulation, by two Escherichia coli supernatant proteins, of the initiation of polypeptide synthesis

Journal Article · · Biochemistry; (United States)
DOI:https://doi.org/10.1021/bi00628a008· OSTI ID:7292468
Two protein factors (A and B) have been partially purified from Escherichia coli supernatant which, in combination, are more effective than 0.5 M NH/sub 4/Cl in stimulating ribosomes for AcPhe-tRNA and fMet-tRNA binding, for the puromycin reaction, and for incorporating acetylphenylalanine from AcPhe-tRNA into polypeptide. The factors appear to differ from the initiation factors, the elongation factor EF-T, and ribosomal proteins. Some uncertainty exists as to whether factor B is different from EF-G. To maximize the effect of the factors in initiator tRNA binding, we preincubated the ribosomes with the factors and carried out the binding assay for a short period at 15/sup 0/C. Maximal stimulation of binding occurred after about a 2-min preincubation at 37/sup 0/C. Longer preincubation times were required at 15/sup 0/C, and only slight stimulation was observed after preincubation at 0/sup 0/C. The extent of stimulation by the factors was not affected when the NH/sub 4/Cl concentration was increased from 40 to 500 mM in the preincubation. The presence of both the 30S and 50S ribosomal subunits is required for the enhancement of AcPhe-tRNA binding. Polyphenylalanine synthesis carried out without AcPhe-tRNA is inhibited by the factors. It is suggested that the factors may act by inducing a structural rearrangement of the ribosomes.
Research Organization:
Univ. of Chicago
OSTI ID:
7292468
Journal Information:
Biochemistry; (United States), Journal Name: Biochemistry; (United States) Vol. 16:9; ISSN BICHA
Country of Publication:
United States
Language:
English