title: Nmag_2608, an extracellular ubiquitin-like domain-containing protein from the haloalkaliphilic archaeon Natrialba magadii.
abstract: Ubiquitin-like proteins (Ubls) and ubiquitin-like domain-containing proteins (Ulds) found in both eukaryotes and prokaryotes display an ubiquitin fold. We previously characterized a 124-amino acid polypeptide (P400) from the haloalkaliphilic archaeon Natrialba magadii having structural homology with ubiquitin family proteins. The reported N. magadii's genome allowed the identification of the Nmag_2608 gene for the protein containing P400, which belongs to specific orthologs of halophilic organisms. It was found that Nmag_2608 has an N-terminal signal peptide with a lipobox motif characteristic of bacterial lipoproteins. Also, it presents partial identity with the ubiquitin-like domain-containing proteins, soluble ligand binding β-grasp proteins. Western blots and heterologous expression tests in E. coli evidenced that Nmag_2608 is processed and secreted outside the cell, where it could perform its function. The analysis of Nmag_2608 expression in N. magadii's cells suggests a co-transcription with the adjoining Nmag_2609 gene encoding a protein of the cyclase family. Also, the transcript level decreased in cells grown in low salinity and starved. To conclude, this work reports for the first time an extracellular archaeal protein with an ubiquitin-like domain.
authors.affiliation: Degradación de Proteínas, Instituto de Investigaciones Biológicas, Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Mar del Plata, CONICET, Funes 3250 CC 1245, 7600, Mar del Plata, Argentina. mvordone@mdp.edu.ar
authors.forename: María Victoria
authors.initials: MV
authors.lastname: Ordóñez
authors.forename: Débora
authors.initials: D
authors.lastname: Nercessian
authors.forename: Rubén Danilo
authors.initials: RD
authors.lastname: Conde
mesh_terms: D020816:Amino Acid Motifs; D019843:Archaeal Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D015870:Gene Expression; D006216:Halobacteriaceae / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins; D040681:Structural Homology, Protein; D025801:Ubiquitin / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism
chemical_list: D019843:Archaeal Proteins; D011994:Recombinant Proteins; D025801:Ubiquitin