Conformational changes in bovine-liver glutamate dehydrogenase: a spin-label study.
A spin-labelled analogue of p-chloromercuribenzoate reacts specifically with glutamate dehydrogenase. The most marked change in the properties of the spin-labelled enzyme is a fivefold decrease in the rate of reduction of the coenzyme by L-glutamate and no change in the rate of oxidation by 2-oxoglutarate. The electron spin resonance spectrum is a sensitive probe for the conformational state of the enzyme. Spin-labelled glutamate dehydrogenase in the presence of saturating concentrations of NADPH and 2-oxoglutarate or L-glutamate shows a complete conformational change while in the presence of NADP+ and 2-oxoglutarate only half of the protomers have changed conformation. The conformational change upon addition of NADPH to the spin-labelled glutamate dehydrogenase in the presence of 2-oxoglutarate happens in a concerted way between 20 and 80% saturation with NADPH. One of the conformations is favoured by the activator ADP while the other is favoured by the inhibitor GTP.
D000818:Animals; D002417:Cattle; D002729:Chloromercuribenzoates / Q000138:chemical synthesis; D005969:Glutamate Dehydrogenase / Q000378:metabolism; D007700:Kinetics; D008099:Liver / Q000201:enzymology*; D009682:Magnetic Resonance Spectroscopy; D009249:NADP / Q000378:metabolism; D011487:Protein Conformation; D013113:Spin Labels; D013696:Temperature
D002729:Chloromercuribenzoates; D013113:Spin Labels; D009249:NADP; D005969:Glutamate Dehydrogenase