title: Sphingomonas paucimobilis beta-glucosidase Bgl1: a member of a new bacterial subfamily in glycoside hydrolase family 1.
abstract: The Sphingomonas paucimobilis beta-glucosidase Bgl1 is encoded by the bgl1 gene, associated with an 1308 bp open reading frame. The deduced protein has a potential signal peptide of 24 amino acids in the N-terminal region, and experimental evidence is consistent with the processing and export of the Bgl1 protein through the inner membrane to the periplasmic space. A His(6)-tagged 44.3 kDa protein was over-produced in the cytosol of Escherichia coli from a recombinant plasmid, which contained the S. paucimobilis bgl1 gene lacking the region encoding the putative signal peptide. Mature beta-glucosidase Bgl1 is specific for aryl-beta-glucosides and has no apparent activity with oligosaccharides derived from cellulose hydrolysis and other saccharides. A structure-based alignment established structural relations between S. paucimobilis Bgl1 and other members of the glycoside hydrolase (GH) family 1 enzymes. At subsite -1, the conserved residues required for catalysis by GH1 enzymes are present in Bgl1 with only minor differences. Major differences are found at subsite +1, the aglycone binding site. This alignment seeded a sequence-based phylogenetic analysis of GH1 enzymes, revealing an absence of horizontal transfer between phyla. Bootstrap analysis supported the definition of subfamilies and revealed that Bgl1, the first characterized beta-glucosidase from the genus Sphingomonas, represents a very divergent bacterial subfamily, closer to archaeal subfamilies than to others of bacterial origin.
authors.affiliation: Centro de Engenharia Biológica e Química, Instituto Superior Técnico, Av. Rovisco Pais, 1049-001 Lisboa, Portugal.
authors.forename: Ana Rita
authors.initials: AR
authors.lastname: Marques
authors.forename: Pedro M
authors.initials: PM
authors.lastname: Coutinho
authors.forename: Paula
authors.initials: P
authors.lastname: Videira
authors.forename: Arsénio M
authors.initials: AM
authors.lastname: Fialho
authors.forename: Isabel
authors.initials: I
authors.lastname: Sá-Correia
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D003001:Cloning, Molecular; D004926:Escherichia coli / Q000235:genetics; D007700:Kinetics; D008969:Molecular Sequence Data; D010802:Phylogeny; D010957:Plasmids / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D020578:Sphingomonas / Q000201:enzymology* / Q000235:genetics; D013329:Structure-Activity Relationship; D001617:beta-Glucosidase / Q000737:chemistry / Q000145:classification / Q000235:genetics* / Q000378:metabolism*
chemical_list: D011993:Recombinant Fusion Proteins; D001617:beta-Glucosidase