Poster #RP218
In silico and in vitro analysis of aspartyl-tRNA synthetase from Halobacterium salinarum
Alexander Machado Cardoso*, Carla Polycarpo**, Dieter Soll**, Orlando Bonifacio Martins*, Ranlig Carvalho Medeiros*, Paulo Ricardo Batista*, Arlan da Silva Goncalves*, Pedro Geraldo Pascutti*
*Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil; **Yale University, New Haven, USA
Aminoacyl-tRNA synthetases (aaRSs) catalyze the transfer of specific amino acids to their corresponding tRNAs to form aminoacyl-tRNAs selecting both amino acid and tRNA substrates with a high degree of precision. However, some aaRSs are not actually capable to discriminate cognate tRNAs. The formation of misaminoacylated Asp-tRNAAsn is essencial for translation in many organisms. Here we show that the Asn-tRNAAsn formation in Halobacterium salinarum, an extreme halophile that grows at near-saturating salinity, occurs via the transamidation of the misaminoacylated Asp-tRNAAsn. The haloarchaea AspRS has a relaxed tRNA specificity that enables it to acylate aspartate into tRNAAsp and tRNAAsn with similar efficiency. To better understand the tRNA specificity and salt tolerance by this ND-AspRS, a theoretical structural model was constructed by comparative modeling using SWISS-MODEL server. Like others halophile proteins this aaRS is highly acidic and negatively charged, as are the tRNA substrates. It is intriguing how this microorganism can do aminoacylation reaction despite the high concentration of salts as an increase in the ionic strength drastically diminishes protein-nucleic interactions and complex formation. Our models also suggest that the histidine (H26) in the b1 strand and proline (P84) in the L1 loop are responsible for tRNAAsn recognition.