title: Molecular characterisation of a thermoactive beta-1,3-glucanase from Oerskovia xanthineolytica.
abstract: Molecular characterisation of a lytic thermoactive beta-1,3-glucanase from Oerskovia xanthineolytica LL-G109 has been performed. A molecular mass of 27 195.6 +/- 1.3 Da and an isoelectric point of 4.85 were determined by electrospray mass spectrometry and from its titration curve, respectively. Its thermoactivity profile shows it to be a heat-stable enzyme with a temperature optimum of 65 degrees C. The secondary structure content of the protein was estimated by circular dichroism to be approx. 25% alpha-helix, 7% random coil, and 68% beta-sheet and beta-turn structure. Nuclear magnetic resonance spectra confirm the high content of beta-structure. Furthermore, the presence of a compact hydrophobic core is indicated by the presence of slowly exchanging amide hydrogens and the enzyme's relatively high resistance to proteolysis. The N-terminal sequences of the intact protein and of a tryptic peptide each exhibit significant similarity to family 16 of glycosyl hydrolases whose overall fold is known to contain almost exclusively beta-sheets and surface loops. Moreover, the sequenced tryptic peptide appears to encompass residues of the Oerskovia xanthineolytica glucanase active site, since it contains a portion of the family 16 active-site motif E-[L/I/V]-D-[L/I/V]-E.
authors.affiliation: New Chemistry Laboratory, University of Oxford, UK.
authors.forename: J
authors.initials: J
authors.lastname: Parrado
authors.forename: P R
authors.initials: PR
authors.lastname: Escuredo
authors.forename: F
authors.initials: F
authors.lastname: Conejero-Lara
authors.forename: M
authors.initials: M
authors.lastname: Kotik
authors.forename: C P
authors.initials: CP
authors.lastname: Ponting
authors.forename: J A
authors.initials: JA
authors.lastname: Asenjo
authors.forename: C M
authors.initials: CM
authors.lastname: Dobson
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D002942:Circular Dichroism; D005656:Fungal Proteins / Q000737:chemistry* / Q000302:isolation & purification; D043326:Glucan 1,3-beta-Glucosidase; D006358:Hot Temperature; D007526:Isoelectric Point; D009682:Magnetic Resonance Spectroscopy; D013058:Mass Spectrometry; D008969:Molecular Sequence Data; D008970:Molecular Weight; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D015003:Yeasts / Q000201:enzymology*; D001617:beta-Glucosidase / Q000737:chemistry* / Q000302:isolation & purification
chemical_list: D005656:Fungal Proteins; D001617:beta-Glucosidase; D043326:Glucan 1,3-beta-Glucosidase