An environment-dependent structural switch underlies the regulation of carnitine palmitoyltransferase 1A.
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Rao JN, Warren GZ, Estolt-Povedano S, Zammit VA, Ulmer TS
An environment-dependent structural switch underlies the regulation of carnitine palmitoyltransferase 1A.
J Biol Chem. 2011 Dec 9;286(49):42545-54. doi: 10.1074/jbc.M111.306951. Epub 2011 Oct 11.
- PubMed ID
- 21990363 [ View in PubMed]
- Abstract
The enzyme carnitine palmitoyltransferase 1 (CPT1), which is anchored in the outer mitochondrial membrane (OMM), controls the rate-limiting step in fatty acid beta-oxidation in mammalian tissues. It is inhibited by malonyl-CoA, the first intermediate of fatty acid synthesis, and it responds to OMM curvature and lipid characteristics, which reflect long term nutrient/hormone availability. Here, we show that the N-terminal regulatory domain (N) of CPT1A can adopt two complex amphiphilic structural states, termed Nalpha and Nbeta, that interchange in a switch-like manner in response to offered binding surface curvature. Structure-based site-directed mutageneses of native CPT1A suggest Nalpha to be inhibitory and Nbeta to be noninhibitory, with the relative Nalpha/Nbeta ratio setting the prevalent malonyl-CoA sensitivity of the enzyme. Based on the amphiphilic nature of N and molecular modeling, we propose malonyl-CoA sensitivity to be coupled to the properties of the OMM by Nalpha-OMM associations that alter the Nalpha/Nbeta ratio. For enzymes residing at the membrane-water interface, this constitutes an integrative regulatory mechanism of exceptional sophistication.