Biophysical characterization Of Alpers encephalopathy associated mutants of human mitochondrial phenylalanyl-tRNA synthetase.

Mutations in nucleus-encoded mitochondrial aminoacyl-tRNA synthetases (mitaaRSs) lead to defects in mitochondrial translation affecting the expression and function of 13 subunits of the respiratory chain complex leading to diverse pathological conditions. Mutations in the FARS2 gene encoding human mitochondrial phenylalanyl-tRNA synthetase (HsmitPheRS) have been found to be associated with two different clinical representations, infantile Alpers encephalopathy and spastic paraplegia. Here we have studied three pathogenic mutants (Tyr144Cys, Ile329Thr, and Asp391Val) associated with Alpers encephalopathy to understand how these variants affect the biophysical properties of the enzyme. These mutants have already been reported to have reduced aminoacylation activity. Our study established that the mutants are significantly more thermolabile compared to the wild-type enzyme with reduced solubility in vitro. The presence of aggregation-prone insoluble HsmitPheRS variants could have a detrimental impact on organellar translation, and potentially impact normal mitochondrial function. © 2019 IUBMB Life, 71(8): 1141-1149, 2019 © 2019 IUBMB Life, 71(8):1141-1149, 2019.