GLOBAL ANALYSIS OF PROTEINS SYNTHESIZED DURING PHOSPHORUS RESTRICTIONIN ESCHERICHIA-COLI

The pattern of proteins synthesized in Escherichia coli during steady- state growth in media with ample inorganic phosphate (P-i), upon limit ation for P-i (without an alternative phosphorous compound), and durin g steady-state growth in media containing phosphonate (PHN) as the sol e P source was examined by two-dimensional gel electrophoresis. Of 816 proteins monitored in these experiments, all those with differential synthesis rates greater than 2.0 or less than 0.5 upon phosphate limit ation (P limitation) or during growth on PHN compared with their rates in the cultures with P-i were classified as belonging to the PL or PH N stimulon, respectively. The PL stimulon included 413 proteins, 208 s howing induced synthesis and 205 showing repressed synthesis. The PHN stimulon was smaller: it included 257 proteins; 227 shelved induced sy nthesis and 30 showed repressed synthesis. The overlap of the two stim ulons included 137 proteins: most (118) were ones showing induced synt hesis. The promoter regions of genes for several of the proteins with induced or repressed synthesis contained sequences which resembled the consensus sequence for PhoB binding. The aggregate mass of proteins r esponding to P limitation or growth on PHN was 30 to 40% of the cells' total mass. By comparing the proteins responding to P limitation with those responding to growth on PHN, one can speculate which proteins a re likely involved in adapting cells to new P sources or in preparing cells to survive stationary phase.