THE INFLUENCE OF GLU44 AND GLU56 OF CYTOCHROME B(5) ON THE PROTEIN-STRUCTURE AND INTERACTION WITH CYTOCHROME-C

The gene encoding trypsin-solubilized bovine liver microsomal cytochro me b(5) (82 residues in length) has been mutated, in which the codons of Glu44 and Glu56 were changed to those of Ala. The mutated genes wer e expressed in Escherichia coli successfully and three mutant proteins (E44A, E56A and E44/56A) were obtained, The UV-visible, CD and H-1 NM R spectra of proteins have been studied, The results show that the mut agenesis at surface residues does not alter the secondary and tertiary structures of cytochrome b(5) significantly, The interactions between recombinant cytochrome b(5) and its mutants with cytochrome c were st udied by using optical difference spectra, The results demonstrated th at both Glu44 and Glu56 of cytochrome b(5) participate in the formatio n of a complex between cytochrome b(5) and cytochrome c.