Poster abstracts

Poster number 121 submitted by Udumbara Rathnayake

Novel protein that optimizes tRNA aminoacylation in Helicobacter pylori

Udumbara M. Rathnayake (Chemistry, Wayne State University), Gayathri Silva (Chemistry, Wayne State University), Tamara L. Hendrickson (Chemistry, Wayne State University)

Abstract:
Helicobacter pylori (H. pylori), the pathogenic bacterium that causes stomach ulcers and gastric cancers, lack genes encoding glutaminyl-tRNA synthetase (GlnRS) and asparaginyl-tRNA synthetase (AsnRS) and consequently rely on an indirect pathway to produce Gln-tRNAGln and Asn-tRNAAsn. The first step for Gln-tRNAGln synthesis involves misacylation of tRNAGln with glutamate to produce Glu-tRNAGln, this reaction is catalyzed by glutamyl-tRNA synthetase 2 (GluRS2). Subsequently, an amidotransferase called AdT converts Glu-tRNAGln to Gln-tRNAGln. An analogous, two step process exists to produce Asn-tRNAAsn. In this case, a non-discriminating aspartyl-tRNA synthetase (ND-AspRS) misacylates tRNAAsn to produce Asp-tRNAAsn, which is then converted to Asn-tRNAAsn by AdT.
Mechanism/s for the quick delivery of Asp-tRNAAsn and Glu-tRNAGln, from the two misacylating aaRSs to AdT must exist in order to ensure the fidelity of protein synthesis. For example, Thermus thermophilus (T. thermoplilus) assembles a stable ribonucleoprotein complex from tRNAAsn, AdT and ND-AspRS called the Asn-transamidosome, which prevents premature release of Asp-tRNAAsn prior to repair by AdT. This mechanism increases the efficient production of Asn-tRNAAsn while minimizing translational errors. Unlike T. thermoplilus, H. pylori require another protein partner, Hp0100, to form a stable, tRNA-independent Asn-transamidosome. Hp0100 accelerates Asn-tRNAAsn production by ~35 fold. Our preliminary evidence suggests that Hp0100 contains two mutually exclusive ATP binding domains, which are activated by Glu-tRNAGln and Asp-tRNAAsn respectively. Further, Hp0100 also has a putative metal binding motif that preferentially binds to divalent metal ions. Initial studies indicate that there may be dual regulation of Hp0100 ATPase activity: by metals and misacylated aa-tRNA.

Keywords: Helicobacter pylori, Hp0100, Asn-transamidosome