Reaction of hemerythrin with disulfides.
The reactions of hemerythrin from Phascolopsis gouldii with the specific sulfhydryl reagents 5,5'-dithiobis(2-nitrobenzoate), 2,2'-dithiodipyridine, and 4,4'-dithiodipyridine were studied at 25 degrees C. Spectrophotometric measurements showed that 1 mol of disulfide reacted per protein subunit consistent with a single cysteine at residue 50. Reaction leads to dissociation of the octameric structure of the native protein to monomers. The first-order rate constants at 25 degrees C and pH 9.0 for reactions of methemerythrin [(1.5 +/- 0.3) X 10(-3) s-1] and metazidohemerythrin [(4.0 +/- 0.3) X 10(-3) s-1] are independent of both the concentration and the nature of the disulfide. The reactions of methemerythrin are strongly inhibited by ClO4-ion, which however has no effect on the rates of those of metazidohemerythrin. The first-order kinetic behavior is ascribed to a conformational change involving the protein controlling the reaction, and this slow change appears to dominate a number of the reactions of hemerythrin.
D015082:2,2'-Dipyridyl / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D004220:Disulfides / Q000494:pharmacology*; D004228:Dithionitrobenzoic Acid / Q000494:pharmacology; D006422:Hemerythrin / Q000378:metabolism*; D007700:Kinetics; D008667:Metalloproteins / Q000378:metabolism*; D009348:Nematoda / Q000378:metabolism*; D011725:Pyridines / Q000494:pharmacology; D013053:Spectrophotometry; D013329:Structure-Activity Relationship; D013439:Sulfhydryl Reagents / Q000494:pharmacology
D004220:Disulfides; D006422:Hemerythrin; D008667:Metalloproteins; D011725:Pyridines; D013439:Sulfhydryl Reagents; C001105:2,2'-dipyridyl disulfide; C004847:3,3'-dipyridyl disulfide; D015082:2,2'-Dipyridyl; D004228:Dithionitrobenzoic Acid