title: The surface layer (S-layer) glycoprotein of Geobacillus stearothermophilus NRS 2004/3a. Analysis of its glycosylation.
abstract: Geobacillus stearothermophilus NRS 2004/3a possesses an oblique surface layer (S-layer) composed of glycoprotein subunits as the outermost component of its cell wall. In addition to the elucidation of the complete S-layer glycan primary structure and the determination of the glycosylation sites, the structural gene sgsE encoding the S-layer protein was isolated by polymerase chain reaction-based techniques. The open reading frame codes for a protein of 903 amino acids, including a leader sequence of 30 amino acids. The mature S-layer protein has a calculated molecular mass of 93,684 Da and an isoelectric point of 6.1. Glycosylation of SgsE was investigated by means of chemical analyses, 600-MHz nuclear magnetic resonance spectroscopy, and matrix-assisted laser desorption ionization-time of flight mass spectrometry. Glycopeptides obtained after Pronase digestion revealed the glycan structure [-->2)-alpha-L-Rhap-(1-->3)-beta-L-Rhap-(1-->2)-alpha-L-Rhap-(1-->](n = 13-18), with a 2-O-methyl group capping the terminal trisaccharide repeating unit at the non-reducing end of the glycan chains. The glycan chains are bound via the disaccharide core -->3)-alpha-l-Rhap-(1-->3)-alpha-L-Rhap-(L--> and the linkage glycose beta-D-Galp in O-glycosidic linkages to the S-layer protein SgsE at positions threonine 620 and serine 794. This S-layer glycoprotein contains novel linkage regions and is the first one among eubacteria whose glycosylation sites have been characterized.
authors.affiliation: Zentrum für Ultrastrukturforschung und Ludwig Boltzmann-Institut für Molekulare Nanotechnologie, Universität für Bodenkultur Wien, A-1180 Wien, Austria. crs@edv1.boku.ac.at
authors.forename: Christina
authors.initials: C
authors.lastname: Schäffer
authors.forename: Thomas
authors.initials: T
authors.lastname: Wugeditsch
authors.forename: Hanspeter
authors.initials: H
authors.lastname: Kählig
authors.forename: Andrea
authors.initials: A
authors.lastname: Scheberl
authors.forename: Sonja
authors.initials: S
authors.lastname: Zayni
authors.forename: Paul
authors.initials: P
authors.lastname: Messner
mesh_terms: D000595:Amino Acid Sequence; D001406:Bacillaceae / Q000235:genetics*; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification; D002240:Carbohydrate Sequence; D006020:Glycopeptides / Q000737:chemistry; D006031:Glycosylation; D008562:Membrane Glycoproteins / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification; D008969:Molecular Sequence Data; D015183:Restriction Mapping; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
chemical_list: D001426:Bacterial Proteins; D006020:Glycopeptides; D008562:Membrane Glycoproteins; C055764:S-layer proteins