OCCURRENCE OF STRUCTURAL HOMOLOGS TO UBIQUITIN IN HALOALKALIPHILIC ARCHAEA

CRISTINA MARINO BUSLJE; DEBORA NERCESSIAN; MARÍA VICTORIA ORDOÑÉZ; ROSANA ESTHER DE CASTRO; RUBÉN DANILO CONDE

INTERNATIONAL MICROBIOLOGY

VIGUERA EDITORES

Año: 2009 vol. 12 p. 167 - 173

1139-6709

SUMMARY Ubiquitin, a widely conserved protein in eukaryotes, takes part in a number of cellular processes, including proteolysis. Sequences encoding ubiquitin-like proteins have not been identified in the prokaryotic genomes sequenced so far, however, they reveal the occurrence of structural and functional homologs to ubiquitin in both Bacteria and Archaea. In this report the amplification and proteomic analysis of a 400 bp DNA fragment from the haloalkaliphilic archaeon Natrialba magadii is described. These studies proved that the encoded polypeptide, denoted as P400, displays structural homology to ubiquitin-like proteins such as ThiS family and Urm1. Moreover, the expression of the P400 DNA sequence in E. coli cells yielded a recombinant polypeptide that reacted with anti-ubiquitin antibodies. Interestingly, a putative open reading frame encoding P400 was identified in the recently sequenced genome of Nab. magadii. Altogether, these results evidence the occurrence of structural homologs to ubiquitin-related proteins in Archaea.