Understanding the basis of pathogenicity in the R592W mutant of human mitochondrial alanyl‐tRNA synthetase

Abstract

We are exploring the effects of recently discovered (Götz, et al., (2011) Am. J. Hum. Genet. 88, 635) pathogenic mutations in human mitochondrial alanyl‐tRNA synthetase (mt AlaRS) on tRNA recognition and enzymatic function. These authors found an R592W mutation in multiple patients with severe infantile cardiomyopathy. R592 lies within the editing domain of mt AlaRS, but is distal to the aminoacyl editing active site. To characterize the editing function of mt AlaRS, we have constructed an editing‐defective C719A/Q622H mutant of the enzyme. While this editing defective mutant effectively mischarges human mt tRNAAla with serine, no accumulation of Ser‐tRNAAla is observed with wildtype or R592W mt AlaRS. We are currently investigating the hypothesis that, rather than disabling the enzyme's ability to hydrolyze misacylated tRNAs, the R592W mutation enables hydrolysis of the correctly acylated Ala‐tRNAAla product in the editing site of mt AlaRS.This work was supported by Carleton College and the Howard Hughes Medical Institute.