The binding of cytochrome b5 to plasma membranes of rat liver: its implication for membrane specificity and biogenesis.

The in vitro incorporation of cytochrome b5 into purified plasma membranes was investigated by biochemical and immunological methods. Plasma membrane preparations incorporated three times less cytochrome b5 than did microsomal preparations; 60% of this cytochrome b5 could not be reduced by the NADH-cytochrome b5 reductase and considered as being bound to the plasma membrane. The morphological observations made after the immunochemical labeling of cytochrome b5 clearly showed a good but asymmetrical distribution of the ferritin labeling: only the inner face of the plasma membrane incorporated cytochrome b5. These results are discussed with respect to theories which concern the subcellular membrane relationships in the cell.