title: Kinectics of beta-galactosidase synthesis in Escherichia coli at 5 C.
abstract: The defect in protein synthesis that is observed in Escherichia coli after transfer to low temperature was studied. For the enzyme beta-galactosidase, the elongation reactions of transcription and translation can take place slowly but normally at 5 C. The time necessary to complete the coupled synthesis of the beta-galactosidase messenger ribonucleic acid and polypeptide chain was found to be about 80 min at 5 C. From this result and from the known length of the beta-galactosidase monomer, it is possible to calculate that at 5 C one amino acid is added to the growing polypeptide chain every 4 s. The initiation of transcription of the beta-galactosidase messenger is inhibited after transfer to 5 C. This fact alone, however, cannot account for all of the phenomena observed at 5 C, because a given amount of messenger yields less enzyme at 5 C than it does at 37 C. Furthermore, in cells induced for short periods at 37 C, the capacity to synthesize beta-galactosidase after transfer to 5 C was found to accumulate linearily with the square of the time of induction. Two alternative models could account for these data. If all ribosomes that initiate translation at 37 C yield complete beta-galactosidase polypeptide chains at 5 C, then an inhibition of translation initiation after transfer to 5 C must be invoked to explain the results. If, on the other hand, a substantial portion of the ribosomes that initiate translation at 37 C do not yield complete beta-galactosidase polypeptides at 5 C, then intracistronic polarity could account for the data, and there is no need to invoke an inhibition of translation initiation at 5 C.
mesh_terms: D001426:Bacterial Proteins / Q000096:biosynthesis; D003080:Cold Temperature; D000242:Cyclic AMP / Q000494:pharmacology; D012321:DNA-Directed RNA Polymerases / Q000378:metabolism; D004790:Enzyme Induction; D004926:Escherichia coli / Q000201:enzymology* / Q000378:metabolism; D005696:Galactosidases / Q000096:biosynthesis* / Q000378:metabolism; D007700:Kinetics; D010452:Peptide Biosynthesis; D010441:Peptide Chain Elongation, Translational; D014176:Protein Biosynthesis; D012329:RNA, Bacterial / Q000096:biosynthesis; D012333:RNA, Messenger / Q000096:biosynthesis; D012293:Rifampin / Q000494:pharmacology; D014158:Transcription, Genetic
chemical_list: D001426:Bacterial Proteins; D012329:RNA, Bacterial; D012333:RNA, Messenger; D000242:Cyclic AMP; D012321:DNA-Directed RNA Polymerases; D005696:Galactosidases; D012293:Rifampin