An Environment-dependent Structural Switch Underlies the Regulation of Carnitine Palmitoyltransferase 1A.Rao, J.N., Warren, G.Z., Estolt-Povedano, S., Zammit, V.A., Ulmer, T.S.
(2011) J Biol Chem 286: 42545-42554
- PubMed: 21990363
- DOI: https://doi.org/10.1074/jbc.M111.306951
- Primary Citation of Related Structures:
- 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 β-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 Nα and Nβ, that interchange in a switch-like manner in response to offered binding surface curvature. Structure-based site-directed mutageneses of native CPT1A suggest Nα to be inhibitory and Nβ to be noninhibitory, with the relative Nα/Nβ 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 Nα-OMM associations that alter the Nα/Nβ ratio. For enzymes residing at the membrane-water interface, this constitutes an integrative regulatory mechanism of exceptional sophistication.
Metabolic and Vascular Health Division, Warwick Medical School, University of Warwick, Gibbet Hill Road, Coventry, CV4 7AL, United Kingdom.