Iron and copper in plasma membranes.

Nonheme iron has been found in pig erythrocyte and mouse liver plasma membranes. The amount found, 8.2 nmol/mg protein in erythrocyte membranes and 7.4 nmol/mg protein in liver plasma membrane, is slightly lower than values reported for endoplasmic reticulum and Golgi apparatus. Less than one-third of the erythrocyte membrane iron can be released by acid treatment, which indicates that most of it is not in the typical iron-sulfur structure. Copper has been found in pig erythrocyte plasma membrane at a concentration of 0.45 nmol/mg protein. These metals may be associated with the redox enzymes of plasma membranes.