KINETIC-ANALYSIS BY IN-VIVO P-31 NUCLEAR-MAGNETIC-RESONANCE OF INTERNAL P-I DURING THE UPTAKE OF SN-GLYCEROL-3-PHOSPHATE BY THE PHO REGULON-DEPENDENT UGP SYSTEM AND THE GLP REGULON-DEPENDENT GLPT SYSTEM

When sn-glycerol-3-phosphate (G3P) is taken up exclusively by the pho regulon dependent Ugp transport system, it can be used as the sole sou rce of P-i but not as the sole source of carbon, We had previously sug gested that the inability of G3P to be used as a carbon source under t hese conditions is due to trans inhibition of G3P uptake by internal P -i derived from the degradation of G3P (P, Brzoska, M. Rimmele, K, Brz ostek, and W, Boos, J, Bacteriol, 176:15-20, 1994). Here, we report P- 31 nuclear magnetic resonance measurements of intact cells after expos ure to G3P as well as to P-i, using different mutants defective in pst (high-affinity P-i transport), ugp (pho dependent G3P transport), glp T (glp-dependent G3P transport), and glpD (aerobic G3P dehydrogenase). When G3P was transported by the Ugp system and when metabolism of G3P was allowed (glpD(+)), P-i accumulated to about 13 to 19 mM, When G3P was taken up by the GlpT system, the preexisting internal P-i pool (w hether low or high) did not change, Both systems were inversly control led by internal P-i, Whereas the Ugp system was inhibited, the GlpT sy stem was stimulated by elevated internal P-i.