Human mitochondrial TyrRS disobeys the tyrosine identity rules

Abstract

Human tyrosyl-tRNA synthetase from mitochondria (mt-TyrRS) presents dual sequence features characteristic of eubacterial and archaeal TyrRSs, especially in the region containing amino acids recognizing the N1-N72 tyrosine identity pair. This would imply that human mt-TyrRS has lost the capacity to discriminate between the G1-C72 pair typical of eubacterial and mitochondrial tRNA^Tyr and the reverse pair C1-G72 present in archaeal and eukaryal tRNA^Tyr. This expectation was verified by a functional analysis of wild-type or mutated tRNA^Tyr molecules, showing that mt-TyrRS aminoacylates with similar catalytic efficiency its cognate tRNA^Tyr with G1-C72 and its mutated version with C1-G72. This provides the first example of a TyrRS lacking specificity toward N1-N72 and thus of a TyrRS disobeying the identity rules. Sequence comparisons of mt-TyrRSs across phylogeny suggest that the functional behavior of the human mt-TyrRS is conserved among all vertebrate mt-TyrRSs.

Keywords

• tRNA identity
• cross-species aminoacylation
• phylogeny
• tRNA acceptor stem
• tyrosylation