Structural and thermodynamic dissection of specific mannan recognition by a carbohydrate binding module, TmCBM27.
The C-terminal 176 amino acids of a Thermotoga maritima mannanase (Man5) constitute a carbohydrate binding module (CBM) that has been classified into CBM family 27. The isolated CBM27 domain, named TmCBM27, binds tightly (K(a)s 10(5)-10(6) M(-1)) to beta-1, 4-mannooligosaccharides, carob galactomannan, and konjac glucomannan, but not to cellulose (insoluble and soluble) or soluble birchwood xylan. The X-ray crystal structures of native TmCBM27, a TmCBM27-mannohexaose complex, and a TmCBM27-6(3),6(4)-alpha-D-galactosyl-mannopentaose complex at 2.0 A, 1.6 A, and 1.35 A, respectively, reveal the basis of TmCBM27's specificity for mannans. In particular, the latter complex, which is the first structure of a CBM in complex with a branched plant cell wall polysaccharide, illustrates how the architecture of the binding site can influence the recognition of naturally substituted polysaccharides.
Boraston
Alisdair B
AB
Department of Chemistry, University of York, Heslington, York YO10 5YW, United Kingdom.
Revett
Timothy J
TJ
Boraston
Catherine M
CM
Nurizzo
Didier
D
Davies
Gideon J
GJ
D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism; D001665:Binding Sites; D002151:Calorimetry; D018360:Crystallography, X-Ray; D008351:Mannans / Q000737:chemistry* / Q000378:metabolism; D008958:Models, Molecular; D015394:Molecular Structure; D009844:Oligosaccharides / Q000378:metabolism*; D011487:Protein Conformation; D013816:Thermodynamics; D020124:Thermotoga maritima; D044902:beta-Mannosidase / Q000737:chemistry* / Q000378:metabolism
D001426:Bacterial Proteins; D008351:Mannans; D009844:Oligosaccharides; D044902:beta-Mannosidase