3pwa

Publication Abstract from PubMed

Cys 126 is a completely conserved residue in triosephosphate isomerase, which is proximal to the active site, but has been ascribed no specific role in catalysis. A previous study of the C126S and C126A mutants of yeast TIM reported substantial catalytic activity for the mutant enzymes leading to suggest that this residue is implicated in folding and stability [Gonzalez-Mondragon et al, (2004) Biochemistry 43, 3255-3263]. We have re-examined the role of Cys 126 using the Plasmodium falciparum enzyme as a model. Five mutants, C126S, C126A, C126V, C126M and C126T have been characterized. Crystal structures of 3-phosphoglycolate (PGA) bound C126S mutant and the unliganded forms of the C126S and C126A mutants have been determined at a resolution of 1.7 A to 2.1 A. Kinetic studies reveal a approximately 5 fold drop in k(cat) for C126S and C126A mutants, while a approximately 10 fold drop is observed for the other three mutants. At ambient temperature, the wild type enzyme and all five mutants show no concentration dependence of activity. At higher temperatures (> 40 degrees C) the mutant enzymes show a significant concentration dependence, with a dramatic loss in activity below 15 muM. The mutant enzymes also have diminished thermal stability at low concentration as monitored by far UV circular dichroism. These results suggest that Cys 126 contributes to the stability of the dimer interface through a network of interactions involving His 95, Glu 97 and Arg 98, which form direct contacts across the dimer interface. Structured digital abstract: Tim binds to Tim by x-ray crystallography (View interaction).

Probing the Role of the Fully Conserved Cys 126 Residue in Triosephosphate Isomerase by Site Specific Mutagenesis. Distal Effects on Dimer Stability.,Samanta M, Banerjee M, Murthy MR, Balaram H, Balaram P FEBS J. 2011 Mar 29. doi: 10.1111/j.1742-4658.2011.08110.x. PMID:21447068^[1]

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