ENZYMATIC AND ELECTRON-TRANSFER ACTIVITIES IN CRYSTALLINE PROTEIN COMPLEXES

Enzymatic and electron transfer activities have been studied by polari zed absorption spectroscopy in single crystals of both binary and tern ary complexes of methylamine dehydrogenase (MADH) with its redox partn ers, Within the crystals, MADH oxidizes methylamine, and the electrons are passed from the reduced tryptophan tryptophylquinone (TTQ) cofact or to the copper of amicyanin and to the heme of cytochrome c(551i) vi a amicyanin, The equilibrium distribution of electrons among the cofac tors, and the rate of heme reduction after reaction with substrate, ar e both dependent on pH, The presence of copper in the ternary complex is not absolutely required for electron transfer from TTQ to heme, but its presence greatly enhances the rate of electron flow to the heme.