title: Conformational analysis of StrH, the surface-attached exo-β-D-N-acetylglucosaminidase from Streptococcus pneumoniae.
abstract: Streptococcus pneumoniae is a serious human pathogen that presents on its surface numerous proteins involved in the host-bacterium interaction. The carbohydrate-active enzymes are particularly well represented among these surface proteins, and many of these are known virulence factors, highlighting the importance of carbohydrate processing by this pathogen. StrH is a surface-attached exo-β-D-N-acetylglucosaminidase that cooperates with the sialidase NanA and the β-galactosidase BgaA to sequentially degrade the nonreducing terminal arms of complex N-linked glycans. This enzyme is a large multi-modular protein that is notable for its tandem N-terminal family GH20 catalytic modules, whose individual X-ray crystal structures were recently reported. StrH also contains C-terminal tandem G5 modules, which are uncharacterized. Here, we report the NMR-determined solution structure of the first G5 module in the tandem, G5-1, which along with the X-ray crystal structures of the GH20 modules was used in conjunction with small-angle X-ray scattering to construct a pseudo-atomic model of full-length StrH. The results reveal a model in which StrH adopts an elongated conformation that may project the catalytic modules away from the surface of the bacterium to a distance of up to ~250 Å.
authors.affiliation: Biochemistry and Microbiology, University of Victoria, Victoria, BC, Canada V8W 3P6.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Pluvinage
authors.forename: Seth
authors.initials: S
authors.lastname: Chitayat
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Ficko-Blean
authors.forename: D Wade
authors.initials: DW
authors.lastname: Abbott
authors.forename: Jobby Maroor
authors.initials: JM
authors.lastname: Kunjachen
authors.forename: Julie
authors.initials: J
authors.lastname: Grondin
authors.forename: Holly L
authors.initials: HL
authors.lastname: Spencer
authors.forename: Steven P
authors.initials: SP
authors.lastname: Smith
authors.forename: Alisdair B
authors.initials: AB
authors.lastname: Boraston
mesh_terms: D000595:Amino Acid Sequence; D020134:Catalytic Domain; D018360:Crystallography, X-Ray; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011485:Protein Binding; D017386:Sequence Homology, Amino Acid; D013296:Streptococcus pneumoniae / Q000201:enzymology*; D013329:Structure-Activity Relationship; D013379:Substrate Specificity; D001619:beta-N-Acetylhexosaminidases / Q000737:chemistry* / Q000378:metabolism
chemical_list: D001619:beta-N-Acetylhexosaminidases