Slabas, A. R. and Kroon, J. T. M. and Scheirer, T. P. and Gilroy, J. S. and Hayman, M. and Rice, D. W. and Turnbull, A. P. and Rafferty, J. B. and Fawcett, T. and Simon, W. J. (2002) 'Squash glycerol-3-phosphate (1)-acyltransferase - Alteration of substrate selectivity and identification of arginine and lysineresidues important in catalytic activity.', Journal of biological chemistry., 277 (46). pp. 43918-43923.
Glycerol-3-phosphate 1-acyltransferase is a soluble chloroplast enzyme involved in glycerol-lipid biosynthesis associated with chilling resistance in plants (1). Resistance is associated with higher selectivity for unsaturated acyl substrates over saturated ones. In vitro substrate selectivity assays performed under physiologically relevant conditions have been established that discriminate between selective and non-selective forms of the enzyme. A mutation, L261F, in the squash protein converts it from a non-selective enzyme into a selective one. The mutation lies within 10 Å of the predicted acyl binding site and results in a higher Km for 16:0 acyl carrier protein (ACP). Site-directed mutagenesis was used to determine the importance of four residues, Arg235, Arg237, Lys193, and His194, implicated to be involved in binding of the phosphate group of glycerol 3-phosphate to the enzyme. All the proteins were highly homologous in structure to the wild type enzyme. Mutations in Arg235, Arg237, and Lys193 resulted in inactive enzyme, while His194 had reduced catalytic activity. The mutant proteins retained the ability to bind stoichiometric quantities of acyl-ACPs supporting the potential role of these residues in glycerol 3-phosphate binding.
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|Publisher Web site:||http://dx.doi.org/10.1074/jbc.M206429200|
|Record Created:||14 May 2007|
|Last Modified:||08 Apr 2009 16:31|
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