5agy

Publication Abstract from PubMed

A library of tau class glutathione transferases (GSTs) was constructed by DNA shuffling using the DNA encoding the Glycine max glutathione transferases Gm GSTU2-2, Gm GSTU4-4, and Gm GSTU10-10. The parental GSTs are > 88% identical at the sequence level, however their specificity varies towards different substrates. The DNA library contained chimeric structures of alternated segments of the parental sequences and point mutations. Chimeric GST sequences were expressed in E. coli and their enzymatic activities towards 1-chloro-2,4-dinitrobenzene (CDNB) and the herbicide fluorodifen (4-nitrophenyl alpha,alpha,alpha-trifluoro-2-nitro-p-tolyl ether) were determined. A chimeric clone (Sh14) with enhanced CDNB and fluorodifen detoxifying activities, and unusual cooperative kinetics towards CDNB and fluorodifen but not towards GSH was identified. The structure of Sh14 was determined at 1.75 angstrom resolution in complex with S -(p-nitrobenzyl)-glutathione. Analysis of the Sh14 structure showed that a Trp114Cys point mutation is responsible for the altered kinetic properties. This was confirmed by the kinetic properties of the Sh14 Cys114Trp mutant. It is suggested that the substitution of the bulky Trp residue by a smaller amino acid (Cys) results in conformational changes of the active site cavity leading to enhanced catalytic activity of Sh14. Moreover, the structural changes allow the strengthening of the two salt bridges between Glu66 and Lys104 at the dimer interface that triggers an allosteric effect and the communication between the H-sites.

Directed Evolution of Tau Class Glutathione Transferases Reveals A Site That Regulates Catalytic Efficiency And Masks Cooperativity.,Axarli I, Muleta AW, Vlachakis D, Kossida S, Kotzia G, Maltezos A, Dhavala P, Papageorgiou AC, Labrou NE Biochem J. 2015 Dec 4. pii: BJ20150930. PMID:26637269^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.