Solution structure of the CBM10 cellulose binding module from Pseudomonas xylanase A.
Plant cell wall hydrolases generally have a modular structure consisting of a catalytic domain linked to one or more noncatalytic carbohydrate-binding modules (CBMs), whose common function is to attach the enzyme to the polymeric substrate. Xylanase A from Pseudomonas fluorescens subsp. cellulosa (Pf Xyn10A) consists of a family 10 catalytic domain, an N-terminal family IIa cellulose-binding module, and an internal family 10 cellulose-binding module. The structure of the 45-residue family 10 CBM has been determined in solution using NMR. It consists of two antiparallel beta-sheets, one with two strands and one with three, with a short alpha-helix across one face of the three-stranded sheet. There is a high density of aromatic residues on one side of the protein, including three aromatic residues (Tyr8, Trp22, and Trp24), which are exposed and form a flat surface on one face, in a classical polysaccharide-binding arrangement. The fold is closely similar to that of the oligonucleotide/oligosaccharide-binding (OB) fold, but appears to have arisen by convergent evolution, because there is no sequence similarity, and the presumed binding sites are on different faces.
Raghothama
S
S
Department of Molecular Biology and Biotechnology, Krebs Institute, University of Sheffield, Sheffield S10 2TN, U.K.
Simpson
P J
PJ
Szabó
L
L
Nagy
T
T
Gilbert
H J
HJ
Williamson
M P
MP
D000595:Amino Acid Sequence; D002482:Cellulose / Q000378:metabolism*; D018360:Crystallography, X-Ray; D043364:Endo-1,4-beta Xylanases; D008024:Ligands; D008969:Molecular Sequence Data; D019906:Nuclear Magnetic Resonance, Biomolecular; D010446:Peptide Fragments / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding / Q000235:genetics; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D011551:Pseudomonas fluorescens / Q000201:enzymology* / Q000235:genetics; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000378:metabolism; D012996:Solutions; D014995:Xylosidases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*
D008024:Ligands; D010446:Peptide Fragments; D011994:Recombinant Proteins; D012996:Solutions; D002482:Cellulose; D014995:Xylosidases; D043364:Endo-1,4-beta Xylanases