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Physicochemical investigation of the chymotrypsins. II. On the mechanism of dimerization of chymotrypsin

1957; Elsevier BV; Volume: 66; Issue: 2 Linguagem: Inglês

10.1016/s0003-9861(57)80011-3

1096-0384

Richard Egan, Harry O. Michel, Robert J. Schlueter, Bernard J. Jandorf,

Insect and Pesticide Research

Summary The sedimentation velocity of α-chymotrypsin was studied as a function of protein concentration and pH. The complete loss of dimerizability for α-chymotrypsin between pH 3.6 and 2.3 points to the involvement of a carboxylate ion—probably contributed by aspartic acid—in the formation of the double molecule of α-chymotrypsin. Loss of ability to dimerize after photooxidation is associated with the destruction of one of the two histidine residues in α-chymotrypsin. The proposition is advanced that a charged imidazolyl group and a carboxylate ion play an essential part in the dimerization of α-chymotrypsin.