SYNTHESIS OF THE BACTERIOPHAGE-LAMBDA-P PROTEIN IN AMINO ACID-STARVEDESCHERICHIA-COLI-CELLS

It was demonstrated previously that in isoleucine-starved Escherichia coli relA mutants harboring a plasmid derived from bacteriophage lambd a the lambda O protein is not synthesized. However, a protein which co precipited with the lambda O during immunoprecipitation with anti-lamb da O serum was synthesized during the relaxed response. Hers we found that this protein is the lambda P gene product. Despite significant in hibition of transcription from the p(R) promoter (which produces mRNA for the lambda P protein synthesis) during the stringent response, the lambda P protein was efficiently synthesized in relA(-) as well as re lA(+) strains starved for isoleucine, threonine and histidine, whereas the synthesis was negligible during starvation for arginine and leuci ne. The synthesis of the lambda P protein in amino acid-starved cells is sensitive to rifampicin. Thus we presume that this phenomenon is no t caused by eventual increased stability of the lambda P mRNA but rath er is an effect of preferential translation of this mRNA and incorpora tion of limited amount of amino acids arising in the starved cells as a result of intracellular proteolysis. One of possible explanations of the mechanism of this phenomenon may suggest that the same signals ca n be recognized in both prokaryotic and eukaryotic cells during initia tion of translation at non-AUG codons. (C) 1996 Academic Press, Inc.