Interaction of a C-terminal peptide of Bos taurus diacylglycerol acyltransferase 1 with model membranes

Diacylglycerol acyltransferase 1 (DGAT1) catalyzes the final and dedicated step in the synthesis of triacylglycerol, which is believed to involve the lipids oleoyl coenzyme A (OCoA) and dioleoyl-sn-glycerol (DOG) as substrates. In this work we investigated the interaction of a specific peptide, referred to as SIT2, on the C-terminal of DGAT1 (HKWCIRHFYKP) with model membranes made with OCoA and DOG in Langmuir monolayers and liposomes. According to the circular dichroism and fluorescence data, conformational changes on SIT2 were seen only on liposomes containing OCoA and DOG. In Langmuir monolayers, SIT2 causes the isotherms of neat OCoA and DOG monolayers to be expanded, but has negligible effect on mixed monolayers of OCoA and DOG. This synergistic interaction between SIT2 and DOG + OCoA may be rationalized in terms of a molecular model in which SIT2 may serve as a linkage between the two lipids. Our results therefore provide molecular-level evidence for the interaction between this domain and the substrates OCoA and DOG for the synthesis of triacylglycerol.     

Solubilisation of oleoyl-CoA thioesterase,oleoyl-CoA: phosphatidylcholine acyltransferase and oleoyl phosphatidylcholine desaturase: The oleate desaturase system of pea leaf microsomes

Membrane-bound enzymes involved in oleate metabolism in microsomes from pea (Pisum sativum L.) leaves were solubilised using detergents, such as n-octyl glucoside, Triton X-100, digitonin or cholate. The detergents were found to be inhibitory to oleoyl-CoA thioesterase, oleoyl-CoA:phosphatidylcholine acyltransferase and oleoyl phosphatidylcholine desaturase. Detergent removal by dialysis resulted in the restoration of activity of both the solubilised oleoyl-CoA thioesterase and oleoyl-CoA:phosphatidylcholine acyltransferase. The putative components of the oleoyl phosphatidylcholine desaturase system were also partially solubilised.     

Alternative NMR method for quantitative determination of acyl positional distribution in triacylglycerols and related compounds

High-resolution 13C NMR spectroscopy has been used to analyze the positional distribution of fatty acids in model triacylglycerols. A novel method for quantitative determination of the positional distribution of unsaturated chains in triacylglycerols simultaneously with the ratio of saturated/unsaturated acyl chains has been proposed, utilizing the chemical shift differences of the aliphatic atoms C4, C5, and C6. The use of HSQC-TOCSY spectra allows unequivocal proof of the position of the unsaturated chain as well as complete assignment of the 13C NMR signals in tripalmitin.