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PMID:17493869

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Citation

Pellon-Maison, M, Montanaro, MA, Coleman, RA and Gonzalez-Baró, MR (2007) Mitochondrial glycerol-3-P acyltransferase 1 is most active in outer mitochondrial membrane but not in mitochondrial associated vesicles (MAV). Biochim. Biophys. Acta 1771:830-8

Abstract

Glycerol 3-phosphate acyltransferase-1 (GPAT1), catalyzes the committed step in phospholipid and triacylglycerol synthesis. Because both GPAT1 and carnitine-palmitoyltransferase 1 are located on the outer mitochondrial membrane (OMM) it has been suggested that their reciprocal regulation controls acyl-CoA metabolism at the OMM. To determine whether GPAT1, like carnitine-palmitoyltransferase 1, is enriched in both mitochondrial contact sites and OMM, and to correlate protein location and enzymatic function, we used Percoll and sucrose gradient fractionation of rat liver to obtain submitochondrial fractions. Most GPAT1 protein was present in a vesicular membrane fraction associated with mitochondria (MAV) but GPAT specific activity in this fraction was low. In contrast, highest GPAT1 specific activity was present in purified mitochondria. Contact sites from crude mitochondria, which contained markers for both endoplasmic reticulum (ER) and mitochondria, also showed high expression of GPAT1 protein but low specific activity, whereas contact sites isolated from purified mitochondria lacked ER markers and expressed highly active GPAT1. To determine how GPAT1 is targeted to mitochondria, recombinant protein was synthesized in vitro and its incorporation into crude and purified mitochondria was assayed. GPAT1 was rapidly incorporated into mitochondria, but not into microsomes. Incorporation was ATP-driven, and lack of GPAT1 removal by alkali and a chaotropic agent showed that GPAT1 had become an integral membrane protein after incorporation. These results demonstrate that two pools of GPAT1 are present in rat liver mitochondria: an active one, located in OMM and a less active one, located in membranes (ER-contact sites and mitochondrial associated vesicles) associated with both mitochondria and ER.

Links

PubMed PMC2230616 Online version:10.1016/j.bbalip.2007.04.001

Keywords

Adenosine Triphosphate/pharmacology; Animals; Biological Markers/metabolism; Cell Fractionation; Complex Mixtures; Endoplasmic Reticulum/drug effects; Endoplasmic Reticulum/enzymology; Endoplasmic Reticulum/metabolism; Glycerol-3-Phosphate O-Acyltransferase/metabolism; Male; Mitochondria, Liver/drug effects; Mitochondria, Liver/enzymology; Mitochondria, Liver/ultrastructure; Mitochondrial Membranes/drug effects; Mitochondrial Membranes/enzymology; Mitochondrial Membranes/ultrastructure; Protein Transport/drug effects; Rats; Rats, Wistar; Submitochondrial Particles/drug effects; Submitochondrial Particles/enzymology; Submitochondrial Particles/ultrastructure

Significance

Annotations

Gene product Qualifier GO Term Evidence Code with/from Aspect Extension Notes Status

RAT:GPAT1

located_in

GO:0005741: mitochondrial outer membrane

ECO:0000314: direct assay evidence used in manual assertion

C

Seeded From UniProt

complete

RAT:GPAT1

part_of

GO:0005741: mitochondrial outer membrane

ECO:0000314: direct assay evidence used in manual assertion

C

Seeded From UniProt

complete


See also

References

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