Conditions restricting allosteric transitions in carp hemoglobin.

摘要: Abstract Below pH 5.6, in the presence of endogenous polyphosphates, carp hemoglobin has a very low ligand affinity, and binding is noncooperative, values n Hill equation being 0.75 1.0 for oxygen carbon monoxide, respectively (Tan, A. L., De Young, A., Noble, R. W. (1972) J. Biol. Chem. 247, 2493–2498). It been postulated that under these conditions molecule remains affinity "deoxy" conformation even when liganded. Raising above 5.6 or removing organic phosphates converts to exhibits usual cooperative binding. Ligand degree cooperativity are phosphate- pH-dependent. Above 8.2 7.5 their absence, ligand-binding properties approach those characteristic again single conformation, only this time with high affinity. Whenever was cooperative, rate CO recombination partially liganded produced by partial flash photolysis faster than fully unliganded full photolysis. Under thought remain one structure, rates upon were equal. The course change relative examined measuring release fluorescent polyphosphate analogue during At there marked lag between dye This decreased finally reversed increased agreement our other results. Kinetic studies combination at wave lengths near Soret isosbestic point revealed difference α β chains hemoglobin. Although results most part can be explained on basis simple two-state model hemoglobin, computer fits reaction could not achieved such simplified scheme, but rather required intra-dimer interactions.