Nmag_2608, an extracellular ubiquitin-like domain containing protein from the haloalkaliphilic archaeon Natrialba magadii

ORDOÑEZ, M. V.; NERCESSIAN, D.; CONDE, R.D.

EXTREMOPHILES

SPRINGER TOKYO

Lugar: Tokyo; Año: 2012 vol. 16 p. 437 - 446

1431-0651

Ubiquitin-like proteins (Ubls) and ubiquitin-likedomain-containing proteins (Ulds) found in botheukaryotes and prokaryotes display an ubiquitin fold. Wepreviously characterized a 124-amino acid polypeptide(P400) from the haloalkaliphilic archaeon Natrialba magadiihaving structural homology with ubiquitin familyproteins. The reported N. magadii?s genome allowed theidentification of the Nmag_2608 gene for the protein containingP400, which belongs to specific orthologs of halophilicorganisms. It was found that Nmag_2608 has anN-terminal signal peptide with a lipobox motif characteristicof bacterial lipoproteins. Also, it presents partialidentity with the ubiquitin-like domain-containing proteins,soluble ligand binding b-grasp proteins. Western blots andheterologous expression tests in E. coli evidenced thatNmag_2608 is processed and secreted outside the cell,where it could perform its function. The analysis ofNmag_2608 expression in N. magadii?s cells suggests a co-transcriptionwith the adjoining Nmag_2609 gene encodinga protein of the cyclase family. Also, the transcript leveldecreased in cells grown in low salinity and starved. Toconclude, this work reports for the first time an extracellulararchaeal protein with an ubiquitin-like domain.