Partial Purification and Characterization of a Blue Light-Sensitive Cytochrome-Flavin Complex from Corn Membranes

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Abstract
A membrane fraction which contains a blue light-sensitive flavine-cytochrome complex (Brain et al.) was partially purified by sucrose and Renografin gradient centrifugations. Assays for marker enzymes show that this membrane fraction is distinct from endoplasmic reticulum, golgi and mitochondria. This membrane fraction co-sedimented with glucan synthetase II activity, a proposed marker for plasma membrane in higher plants. The purified membrane fraction shows virtually identical light minus dark and dithionite reduced minus oxidized difference spectra with difference bands near 427 and 557 nm, suggesting that contamination by other cytochrome-containing membrane fractions is not significant. The photoactivity can be completely solubilized by 0.1% Triton X-100, leaving the bulk of the membrane undissolved. The kinetics for cytochrome photoreduction are not significantly affected by solubilization, indicating that both flavine and cytochrome could be associated with the same protein moiety.