Department of Biology, Revelle College University of California, San Diego, La Jolla, Calif. 92037, U.S.A.
Abstract:
Irradiation of starved cultures of Saccharomyces cerevisiae with blue light under aerobic conditions inhibited the capacity of the yeast cells to respire added substrates (e.g., ethanol) and stimulated endogenous respiration. Spectroscopic examination of the cells showed that the irradiation destroyed both cytochrome a and a3 components of cytochrome oxidase and a part of the cytochrome b. Irradiation under anaerobic conditions had no effect on the respiratory capacity or the cytochrome content of the cells. Under aerobic conditions cytochrome a3 was protected against photodestruction when complexed with cyanide and cytochrome a was protected when complexed with azide.