CONICET | Buscador de Institutos y Recursos Humanos

Ubiquitin is a highly conserved protein that takes part in important processes within eukaryotes, but is not present in prokaryotes. However, both eukaryotic and prokaryotic cells contain ubiquitin like proteins (Ubls), which share similar folding and role with ubiquitin. We previously found proteins recognized by anti-ubiquitin antibodies plus a PCR-product codifying for a peptide with ubiquitin-like structure in haloalkaliphilic archaea. Based on these results, a search for proteins that react with the antibody against ubiquitin was performed in several halophilic archaea and bacteria. For this, microorganisms growth was followed by estimation of OD600, and DNA, RNA, and protein contents. Protein extracts were separated by 1D SDS-PAGE and subjected to Western blot test using a polyclonal anti-ubiquitin antibody. All samples displayed immuno-reactive bands and these results were confirmed by 2D gel electrophoresis. Four most characteristic reactive spots (Mr 50-55 kDa and Ip 3-4) were excised from the gel and subjected to protein sequence determination. The analysis of a 53 kDa spot from Halobacterium halobium showed that it corresponds to the elongation factor EF-1α, which is not an Ubl but takes part in misfolded protein degradation mediated by ubiquitin. Its relationship with Ubls is being analyzed. Supported by CONICET and UNMdP.