INCORPORATION OF CHOLINE INTO OUTER AND INNER MEMBRANES OF ISOLATED RAT LIVER MITOCHONDRIA

Separation of the inner and outer membranes following incubation of mitochondria with 14C‐labelled choline chloride revealed the specific radioactivity both per mg protein and per μg phospholipid phosphorus to be greater in the outer membrane. Under the present conditions of incubation, the incorporation into the microsome fraction was less than 10% (on a mg protein basis) of that into the isolated mitochondria. Labelled choline is also incorporated into the membrane components of isolated mitochondrial fractions, but to a lesser extent than that incorporated into the membranes of intact mitochondria, and in different proportions. The phospholipid phosphorus contents of the “pure” outer and “pure” inner membranes of isolated rat liver mitochondria are respectively about 18.3 and 6.1 μg phosphorus per mg protein. The data are discussed with particular refernce to the biosynthesis of the mitochondrial membranes and to the biogenesis of mitochondria. Copyright © 1968, Wiley Blackwell. All rights reserved