(The) interaction of mitochondrial aspartate aminotransferase with negatively charged phospholipid vesicles

Abstract

Mitochondrial aspartate aminotransferase(m-AAT) is known as a special transport protein which goes into the matrix side of isolated mitochondria through the membrane in vitro. In order to understand the transport mechanism of m-AAT, a pH dependent binding test has been performed. It was found that the binding of m-AAT was maximum at pH 4 but no appreciable binding was observed at neutral pH in the CL:PC 60\% vesicles. The transport of m-AAT across the bilayer was not detected in all pH range studied. The binding pattern of cytosolic aspartate aminotransferase was different from that of mitochondrial isozyme. A detectable amount of binding of cytosolic isozyme was observed at neutral pH. The irreversible binding was observed only at pH 4, and the segment of the enzyme which penetrates into the bilayer was identified by hydrophobic labeling with dansyl chloride.