Semisynthesis of mutant cytochromes c replaced by non-natural aromatic amino acid at Phe82 and photoregulation of reduction reaction with 2-mercaptoethanol

Abstract

Mutant cytochromes c, PGL-Cytc and PYR-Cytc, where Phe82 was replaced respectively with a nonnatural amino acid, N-phenylglycine (pheGly) and 3-(pyren-1-yl)-L-alanine (pyrAla), were synthesized by a semisynthetic method. CD measurements revealed that PGL-Cytc nearly retained the tertiary structure of the native cytochrome c, whilst PYR-Cytc did not. The reduction of PGLCytc by 2-mercaptoethanol was retarded compared with that of the native cytochrome c. On the other hand, PYR-Cytc was easily reduced by 2-mercaptoethanol, probably due to structural changes around the haem moiety and interaction of the pyrenyl group with the haem. Excitation of the pyrenyl group of PYR-Cytc upon UV irradiation suppressed the reduction greatly. This is ascribed to the appearance of oxidation from iron(II) to iron(III) haem through photosensitization of the pyrenyl group.