1xmc
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C323M mutant structure of mouse carnitine octanoyltransferase
OverviewOverview
Carnitine acyltransferases have crucial functions in fatty acid, metabolism. Members of this enzyme family show distinctive substrate, preferences for short-, medium- or long-chain fatty acids. The molecular, mechanism for this substrate selectivity is not clear as so far only the, structure of carnitine acetyltransferase has been determined. To further, our understanding of these important enzymes, we report here the crystal, structures at up to 2.0-A resolution of mouse carnitine, octanoyltransferase alone and in complex with the substrate, octanoylcarnitine. The structures reveal significant differences in the, acyl group binding pocket between carnitine octanoyltransferase and, carnitine acetyltransferase. Amino acid substitutions and structural, changes produce a larger hydrophobic pocket that binds the octanoyl group, in an extended conformation. Mutation of a single residue (Gly-553) in, this pocket can change the substrate preference between short- and, medium-chain acyl groups. The side chains of Cys-323 and Met-335 at the, bottom of this pocket assume dual conformations in the substrate complex, and mutagenesis studies suggest that the Met-335 residue is important for, catalysis.
About this StructureAbout this Structure
1XMC is a Single protein structure of sequence from Mus musculus with EPE and MPD as ligands. Active as Carnitine O-octanoyltransferase, with EC number 2.3.1.137 Full crystallographic information is available from OCA.
ReferenceReference
Crystal structure of mouse carnitine octanoyltransferase and molecular determinants of substrate selectivity., Jogl G, Hsiao YS, Tong L, J Biol Chem. 2005 Jan 7;280(1):738-44. Epub 2004 Oct 17. PMID:15492013
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