Presence of structural homologs to ubiquitin in haloalkaliphilic Archaea

DÉBORA NERCESSIAN; CRISTINA MARINO BUSLJE; MARÍA V. ORDÓÑEZ; ROSANA E. DE CASTRO; RUBÉN D. CONDE

INTERNATIONAL MICROBIOLOGY

VIGUERA EDITORES

Año: 2009 vol. 12 p. 167 - 173

1139-6709

Ubiquitin, a protein widely conserved in eukaryotes, is involved in many cellular processes, including proteolysis. Sequences encoding ubiquitin-like proteins have not been identified in the prokaryotic genomes sequenced so far. However, they reveal the presence of structural and functional homologs of ubiquitin in both Bacteria and Archaea. This work describes the amplification and proteomic analysis of a 400-bp DNA fragment from the haloalkaliphilic archaeon Natrialba magadii. The encoded polypeptide, marked as P400, displayed structural homology to ubiquitin-like proteins such as ThiS family and Urm1. Also, expressing the P400 DNA sequence in Escherichia coli cells yielded a recombinant polypeptide that reacted with anti-ubiquitin antibodies. In addition, a putative open reading frame encoding P400 was identified in the recently sequenced genome of N. magadii. Altogether, these results evidence the presence of structural homologs to ubiquitin-related proteins in Archaea. [Int Microbiol 2009; 12(3):XXX-XXX]