title: Lecithin retinol acyltransferase forms functional homodimers.
abstract: Membrane-bound lecithin retinol acyltransferase (LRAT), an essential enzyme in vitamin A processing, catalyzes the formation of retinyl esters from vitamin A and lecithin. Cloned and expressed LRAT has a molecular mass of 25.3 kDa. The enzyme is not homologous to known enzymes and is, therefore, of substantial interest mechanistically. Along these lines, the functional protomeric state of LRAT is of importance. Gel electrophoretic studies on LRAT in the presence of SDS and disulfide reducing agents show the expected 25 kDa monomer. However, gel electrophoresis in the absence of a reducing agent and/or strong denaturing conditions reveals substantial dimer formation. LRAT monomers can be efficiently and irreversibly cross-linked by thiol reactive bismaleimides in retinal pigment epithelial (RPE) membranes generating LRAT homodimers. Cross-linked LRAT homodimers are fully active catalytically. The experiments suggest that LRAT monomers interact in membranes and form functional homodimers through protein-protein interactions and disulfide bond formation.
authors: Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, 45 Shattuck Street, Boston, Massachusetts 02115, USA.
authors: Wan Jin
authors: WJ
authors: Jahng
authors: Eric
authors: E
authors: Cheung
authors: Robert R
authors: RR
authors: Rando
mesh_terms: D000217:Acyltransferases / Q000737:chemistry* / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D002384:Catalysis; D002417:Cattle; D002462:Cell Membrane / Q000201:enzymology; D003432:Cross-Linking Reagents / Q000737:chemistry / Q000378:metabolism; D019281:Dimerization; D004229:Dithiothreitol / Q000737:chemistry / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D004789:Enzyme Activation; D007700:Kinetics; D008969:Molecular Sequence Data; D010857:Pigment Epithelium of Eye / Q000201:enzymology
chemical_list: D003432:Cross-Linking Reagents; D000217:Acyltransferases; C056942:lecithin-retinol acyltransferase; D004229:Dithiothreitol