The phosphoenolpyruvate: glycose phosphotransferase system, or PTS, comprises a complex array of interacting cytoplasmic and membrane proteins with diverse functions in the bacterial cell. The system mediates concomitant phosphorylation and translocation of PTS sugar substrates across the cytoplasmic membrane, is involved in chemotaxis toward PTS sugars, regulates adenylate cyclase, and regulates permeases that take up certain non-PTS sugars and other solutes (as in diauxic growth). The PTS is widely distributed among obligate and facultative anaerobes, and we have recently shown that it is ubiquitously distributed among common marine bacteria. Thus, the PTS has broad ecological and medical implications, and is also an excellent model of how cytoplasmic proteins regulate the functions of membrane proteins by cycles of phosphorylation/dephosphorylation. We shall continue to study the following problems: (a) Precisely what is the mechanism by which the PTS translocates its substrates across the membrane? (b) The transport function of the PTS is under stringent metabolic control. What mechanisms are involved in this metabolic regulation? (c) What are the mechanisms that control genetic regulation of the pts operons? (d) A functional gene called pel is required for lambda DNA penetration of the inner bacterial membrane: pel was though to encode the PTS membrane protein II-BMan. Cloning studies show, however, that pel encodes a novel protein, Pel, and that Pel is required for both DNA penetration and for mannose phosphorylation. What is the role of Pel in these functions? (e) How does the PTS regulate the E. coli lactose permease and adenylate cyclase? (f) Is the PTS a primordial solute transport system that was modified during evolution to many different transport systems? A combination of biochemical, physico-chemical, and molecular biology methods will be used in attempts to answer these questions.
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