Structures and physiological roles of 13 integral lipids of bovine heart cytochrome c oxidase

Abstract

All 13 lipids, including two cardiolipins, one phosphatidylcholine, three phosphatidylethanolamines, four phosphatidylglycerols and three triglycerides, were identified in a crystalline bovine heart cytochrome c oxidase (CcO) preparation. The chain lengths and unsaturated bond positions of the fatty acid moieties determined by mass spectrometry suggest that each lipid head group identifies its specific binding site within CcOs. The X-ray structure demonstrates that the flexibility of the fatty acid tails facilitates their effective space-filling functions and that the four phospholipids stabilize the CcO dimer. Binding of dicyclohexylcarbodiimide to the O 2 transfer pathway of CcO causes two palmitate tails of phosphatidylglycerols to block the pathway, suggesting that the palmitates control the O 2 transfer process.The phosphatidylglycerol with vaccenate (cis-D 11 -octadecenoate) was found in CcOs of bovine and Paracoccus denitrificans, the ancestor of mitochondrion, indicating that the vaccenate is conserved in bovine CcO in spite of the abundance of oleate (cis-D 9 -octadecenoate). The X-ray structure indicates that the protein moiety selects cis-vaccenate near the O 2 transfer pathway against trans-vaccenate. These results suggest that vaccenate plays a critical role in the O 2 transfer mechanism.

Dimer interface of bovine cytochrome c oxidase is influenced by local posttranslational modifications and lipid binding

“…The lipids associated with dimeric CcO constitute 25 kDa. Assuming that both individual monomers are stabilized by lipids, about six phospholipids likely stabilize the dimeric interface; specifically, CL is thought to stabilize the dimeric CcO interface (11,14,29,30). Recent molecular dynamics simulations identified seven binding sites for CL in CcO (29), most of which are contradictory to sites identified from crystal structures (11,15).…”

“…Two cardiolipins (CL), one phosphatidylcholine (PC), three phosphatidylethanolamines (PE), four phosphatidylglycerols (PG), and three triglycerides (TG) have been identified in bovine crystalline CcO (11). Ether phospholipid choline plasmalogens, typically present in mammalian cell membranes, were also identified but were found to be identical to the corresponding PCs and likely are derivatives thereof (11).…”

“…Two cardiolipins (CL), one phosphatidylcholine (PC), three phosphatidylethanolamines (PE), four phosphatidylglycerols (PG), and three triglycerides (TG) have been identified in bovine crystalline CcO (11). Ether phospholipid choline plasmalogens, typically present in mammalian cell membranes, were also identified but were found to be identical to the corresponding PCs and likely are derivatives thereof (11). Several lipids were also identified that bridge the two CcO monomers, suggesting that they may stabilize a putative dimer interface (11,12), and a critical role for CL has been proposed following its removal and concomitant inactivation of the enzyme (13,14).…”

Specific roles of phosphatidylglycerols in hosts and microbes

“…From determination of crystal structures, not only cardiolipin but also PG are integral components of complexes III and IV of the mitochondria of yeast and mammalian cells (47). In plants, PG can be synthesized in the chloroplast, mitochondria and ER, and is the only major phospholipid present in thylakoid membranes, the site of the light-dependent reactions of photosynthesis.…”

Formation and Fragmentation of Unsaturated Fatty Acid [M – 2H + Na]– Ions: Stabilized Carbanions for Charge-Directed Fragmentation

“…Within phospholipids, the hydrophobic fatty acid acyl chains are crucial in forming biological membranes where they may establish specific interactions with membrane proteins [2,3].…”