The carnitine shuttle consists of a carnitine O-palmitoyltransferase whd localized in the mitochondrial outer membrane, the carnitine:acylcarnitine translocase colt, an integral inner membrane protein, and another carnitine O-palmitoyltransferase CPT2 localized on the matrix side of the inner membrane. The shuttle mediates the transport of activated long-chain fatty acyl-CoAs into the mitochondrial matrix where they undergo beta-oxidation. (Adapted from FBrf0247638.)