title: Influence of "energization" on the binding of M protein with p-nitrophenyl alpha-D-galactopyranoside.
abstract: A specific binding of p-nitrophenyl alpha-D-galactopyranoside has been measured by flow dialysis with Escherichia coli ML 308225 membrane vesicles containing the lac carrier protein. The number of binding sites, 0.45 nmol/mg of membrane protein, remains unchanged in the presence or absence of energy. On the other hand, "energization" increases the M protein affinity for p-nitrophenyl alpha-D-galactopyranoside. The dissociation constant (Kd) is 4 and 21 microM in the presence and absence, respectively, of D-lactate. The same energization effects are found with E. coli A3245 membrane vesicles. p-Nitrophenyl alpha-D-galactopyranoside can be used as a substrate to study energization effect on binding to the lactose permease M protein. These results corroborate observations that energy increases the lac carrier protein affinity for its substrate, and they also confirm the concentration of the M protein, which corresponds to 1.4% of the membrane protein.
mesh_terms: D001665:Binding Sites; D001692:Biological Transport; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D004926:Escherichia coli / Q000378:metabolism*; D029968:Escherichia coli Proteins; D005033:Ethylmaleimide / Q000494:pharmacology; D006027:Glycosides; D007700:Kinetics; D007785:Lactose / Q000378:metabolism; D026901:Membrane Transport Proteins / Q000378:metabolism*; D009004:Monosaccharide Transport Proteins; D009154:Mutation; D009598:Nitrophenylgalactosides; D011485:Protein Binding; D027981:Symporters; D013862:Thiogalactosides / Q000378:metabolism
chemical_list: D029968:Escherichia coli Proteins; D006027:Glycosides; C050221:LacY protein, E coli; D026901:Membrane Transport Proteins; D009004:Monosaccharide Transport Proteins; D027981:Symporters; D013862:Thiogalactosides; D009598:Nitrophenylgalactosides; C021499:lactose permease; D007785:Lactose; D005033:Ethylmaleimide