Characterization of Gtf1p, the Connector Subunit of Yeast Mitochondrial tRNA-dependent Amidotransferase

Abstract

The bacterial GatCAB operon for tRNA-dependent amidotransferase (AdT) catalyzes the transamidation of mischarged glutamyl-tRNA Gln to glutaminyl-tRNA Gln . Here we describe the phenotype of temperature-sensitive (ts) mutants of GTF1, a gene proposed to code for subunit F of mitochondrial AdT in Saccharomyces cerevisiae. The ts gtf1 mutants accumulate an electrophoretic variant of the mitochondrially encoded Cox2p subunit of cytochrome oxidase and an unstable form of the Atp8p subunit of the F 1 -F 0 ATP synthase that is degraded, thereby preventing assembly of the F 0 sector. Allotopic expression of recoded ATP8 and COX2 did not significantly improve growth of gtf1 mutants on respiratory substrates. However, ts gft1 mutants are partially rescued by overexpression of PET112 and HER2 that code for the yeast homologues of the catalytic subunits of bacterial AdT. Additionally, B66, a her2 point mutant has a phenotype similar to that of gtf1 mutants. These results provide genetic support for the essentiality, in vivo, of the GatF subunit of the heterotrimeric AdT that catalyzes formation of glutaminyl-tRNA

Expression of Nuclear and Mitochondrial Genes Encoding ATP Synthase Is Synchronized by Disassembly of a Multisynthetase Complex

“…Since inactivation of mitochondrial translation in yeast leads to the loss of functional mtDNA (Barros et al, 2011), it can be inferred that the ARC cells still import enough cERS molecules into their mitochondria to maintain an efficient organellar protein synthesis activity. Not surprisingly, no deleterious effects on mitochondrial function were observed when both aaRSs were prevented from interacting with Arc1p by the simultaneous competitive binding of peptides that correspond to their respective N-terminal Arc1p-binding domains (nE/nM strain), which in fact mimics what normally occurs in yeast cells adapting to respiration.…”

Glutamyl-tRNA in Bacteria. Multiple Identities for Multiple Functions

“…The formation of macromolecular complexes that compartmentalize certain functions facilitate the routing of part of Glu-tRNA to pathways less abundant than the translation machinery and prevents the leakage of intermediary products that are toxic to the cell such as Glu-tRNA Gln . 89 Nevertheless, a small leakage of Glu-tRNA Gln or Asp-tRNA Asn might not be as toxic as originally supposed. Although protein synthesis has an error rate of only 1 in 10000, E. coli cells allow the incorporation of up to ≈ 10 % erroneous Asp in positions of Asn, thanks to chaperons and proteases that prevent the damage produced by incorrectly folded polypeptides.…”

The Putative GTPase Encoded by MTG3 Functions in a Novel Pathway for Regulating Assembly of the Small Subunit of Yeast Mitochondrial Ribosomes

“…Temperature-sensitive mutants tend to be sufficiently leaky to preserve a large percentage of ϩ cells, even when they are grown at the restrictive temperature (27). Temperature-sensitive mtg3 mutants were obtained by PCR amplification of MTG3 under mutagenic conditions.…”