Strong binding of cytochrome C on the envelope of spinach chloroplasts.

Yeast cationic ferricytochrome c was able to bind to the spinach (Spinacia oleracea) chloroplast envelope with a low affinity (Kd = 1.1 mum). The total amount of low affinity binding sites was of the order of 50 nmol cytochrome c mg(-1) protein. We gave the evidence that binding of ferricytochrome c to the envelope was electrostatic and that the envelope membranes were strongly negatively charged. Addition of yeast ferricytochrome c to a preparation of intact washed chloroplasts (class I) induced a strong agglutination of chloroplasts.