Interaction of mitochondrial malate dehydrogenase monomer with phospholipid vesicles

Publisher Website
Google Scholar
Abstract
The association between bovine and porcine mitochondrial malate dehydrogenase (EC 1.1.1.37) and phospholipid vesicles was investigated. At concentrations at which malate dehydrogenase exists as a dimer, entrapment in the aqueous compartment but not binding of the 14C-labeled enzyme was observed. The dissociated enzyme was labile to moderate heat and to p-chloromercuribenzoate. In both cases, however, inactivation was decreased by incubation with suspensions of charged phospholipid vesicles. An interaction between enzyme subunits and phospholipid was suggested. This was confirmed by direct binding measurements and by studies that followed changes in the fluorescein-labeled enzyme. The circular-dichroism spectra of the enzyme indicated a high .alpha.-helix content and suggested that a small conformational change occurred when the enzyme dissociated. Fluorescence data also suggested less-rigid molecules after dissociation. A possible mechanism based on the flexibility of enzyme monomer and its interaction with phospholipids, by which mitochondrial matrix enzymes are specifically localized in cells, is discussed.