The interaction of ferrocytochrome c with long-chain fatty acids and their CoA and carnitine esters.
Non-covalent modification of cytochrome c may have implications for electron transport and energy metabolism. We examined the interaction of various fatty acids (FAs), their coenzyme A and carnitine esters, and fatty alcohols with horse heart ferrocytochrome c. A comparison of FAs indicated a minimum chain length of 14 carbons was required for significant effect on the ferroheme chromophore and major changes in electronic spectra. Coenzyme A and carnitine esters interacted less strongly than FAs whereas long-chain alcohols did not interact with the protein. We found a single, saturable FA binding site with Kd (oleate) of 23.1 microM (by stopped-flow kinetics), 30 microM (by radiochemical binding assay), and 29 microM (by spectrophotometric assay). The binding stoichiometry was 1:1. We present evidence from electronic spectra, and proton NMR (nuclear magnetic resonance) that the S-Fe coordination (methionine 80) was disrupted by ligand binding. From molecular modeling we identify a putative binding channel flanked by lysines 72 and 73.
Stewart
J M
JM
Department of Biology, Mount Allison University, Sackville, NB, Canada. jstewart@mta.ca
Blakely
J A
JA
Johnson
M D
MD
D000214:Acyl Coenzyme A / Q000378:metabolism*; D000818:Animals; D002331:Carnitine / Q000031:analogs & derivatives* / Q000378:metabolism*; D003574:Cytochrome c Group / Q000737:chemistry / Q000378:metabolism*; D005227:Fatty Acids / Q000378:metabolism*; D005233:Fatty Alcohols / Q000378:metabolism; D006736:Horses; D008024:Ligands; D019906:Nuclear Magnetic Resonance, Biomolecular; D019301:Oleic Acid / Q000378:metabolism*; D010172:Palmitoylcarnitine / Q000378:metabolism; D013057:Spectrum Analysis
D000214:Acyl Coenzyme A; D003574:Cytochrome c Group; D005227:Fatty Acids; D005233:Fatty Alcohols; D008024:Ligands; C116917:acylcarnitine; D010172:Palmitoylcarnitine; D019301:Oleic Acid; D002331:Carnitine