Poster abstracts

Poster number 37 submitted by Shirin Fatma

A Small protein that interacts with EF-Tu, GluRS2 and small molecules

Shirin Fatma (Chemistry, Wayne State Univetsity), Keng-Ming Chang (Chemistry, Wayne State Univetsity), Tamara Hendrickson (Chemistry, Wayne State Univetsity)

Abstract:
A Small protein that interacts with EF-Tu, GluRS2 and small molecules
Shirin Fatma, Keng-Ming Chang and Tamara L. Hendrickson*
Department of Chemistry, Wayne State University, 5101 Cass Avenue, Detroit, MI 48202. USA.shirin@chem.wayne.edu

Maintaining the fidelity of protein biosynthesis is crucial to all life but offers unique challenges in organisms missing one or more of the aminoacyl-tRNA synthetases (aaRSs). H. pylori, an ɛ-proteobacterium, is missing both glutaminyl-tRNA synthetase (GlnRS) and asparaginyl-tRNA synthetase (AsnRS) and synthesizes both Gln-tRNAGln and Asn-tRNAAsn by an indirect aminoacylation pathway. To generate Asn-tRNAAsn, tRNAAsn is mischarged by a non-discriminating aspartyl-tRNA synthetase (ND-AspRS). Next, Asp-tRNAAsn is converted to Asn-tRNAAsn by an amidotransferase (AdT). However, for production of Gln-tRNAGln, H. pylori have two functional copies of gltX, the gene encoding for glutamyl-tRNA synthetase. GluRS2 specifically generates Glu-tRNAGln, which is subsequently converted to Gln-tRNAGln by the same AdT. Partly because of these misacylation pathways, protein biosynthesis includes different proofreading checkpoints (e.g. within the aaRSs, EF-Tu, and the ribosome).
We are examining proteins of unknown functions that were identified by yeast two-hybrid (Y2H) as potential new players in tRNA aminoacylation (both direct and indirect) and fidelity. These efforts have identified Hp0495 as a possible participant. Hp0495 binds ATP, glutamate, and either tRNAGlu1 or tRNAGln. It also forms a complex with EF-Tu and a tRNAGln-dependent complex with GluRS2. These results suggest that Hp0495 plays a role in preventing Glu-tRNAGln complex formation with EF-Tu or in delivering this misacylated tRNA to AdT. The possible consequences of these ribonucleoprotein complexes on tRNA aminoacylation, transamidation, and translational fidelity will be discussed. Existence of these proteins of unknown function and their interactions with components of the translation machinery clearly demonstrates that the classical boundaries of the field of tRNA aminoacylation need to be expanded.

Keywords: EF-Tu