The long-term objective of this investigation is to understand the role of mitochondrial outer membrane in cells. In this project, attention will be focused on glycerophosphate acyltransferase which synthesizes lysophosphatidic acid. Recent data have shown that mitochondria can export lysophosphatidic acid. It will be determined if lysophosphatidic acid exported by mitochondria can be converted to phosphatidic acid and complex phospholipids by microsomes. If so, the process offers an excellent mechanism of how cells regulate the selective positioning of fatty acids found in glycerophospholipids. The metabolic fate of mitochondrially made phosphatidic acid will be determined to see if it is used by the microsomes or mitochondria or both to make complex phospholipids. Specific cytosolic proteins will be studied as to their involvement in the export of mitochondrially made lysophosphatidic acid. Glycerophosphate acyltransferase will be purified and its topography studied by probing the outer and inner surface of the outer membrane with proteases and lactoperoxidase iodination.%%% The work is important in cell biology because it will lead to an understanding of the significance of phospholipid synthesis by the mitochondrial outer membrane and the regulation of asymmetric distribution of fatty acids in cell phospholipids. The outer mitochondrial membrane is very difficult to study because it is very difficult to isolate in sufficient quantity. Dr. Haldar has pioneered methods to overcome this problem. This membrane is important to study because many proteins must pass through to reach their site of action in the cell.*** //
