The three-dimensional structure of native xylanase A from Pseudomonas flouorescens subspecies cellulosa has been refined at 1.8 A resolution. The space group is P2(1)2(1)2(1) with four molecules in the asymmetric unit. The final model has an R factor of 0 ...
The three-dimensional structure of native xylanase A from Pseudomonas flouorescens subspecies cellulosa has been refined at 1.8 A resolution. The space group is P2(1)2(1)2(1) with four molecules in the asymmetric unit. The final model has an R factor of 0.166 for 103 749 reflections with the four molecules refined independently. The tertiary structure consists of an eightfold beta/alpha-barrel, the so-called TIM-barrel fold. The active site is in an open cleft at the carboxy-terminal end of the beta/alpha-barrel, and the active-site residues are a pair of glutamates, Glu127 on strand 4 and Glu246 on strand 7. Both these catalytic glutamate residues are found on beta-bulges. An atypically long loop after strand 7 is stabilized by calcium. Unusual features include a non-proline cis-peptide residue Ala80 which is found on a beta-bulge at the end of beta-strand 3. The three beta-bulge type distortions occurring on beta-strands 3, 4 and 7 are functionally significant as they serve to orient important active-site residues. The active-site residues are further held in place by an extensive hydrogen-bonding network of active-site residues in the catalytic site of xylanase A. A chain of well ordered water molecules occupies the substrate-binding cleft, some or all of which are expelled on binding of the substrate.
Related Citations:
Beta-Glucosidase, Beta-Galactosidase, Family a Cellulases, Family F Xylanases and Two Barley Glycanases Form a Superfamily of Enzymes with 8-Fold Beta/Alpha Architecture and with Two Conserved Glutamates Near the Carboxy-Terminal Ends of Beta-Strands Four and Seven Jenkins, J., Lo Leggio, L., Harris, G., Pickersgill, R. (1995) FEBS Lett 362: 281
Structure of the Catalytic Core of the Family F Xylanase from Pseudomonas Fluorescens and Identification of the Xylopentaose-Binding Sites Harris, G.W., Jenkins, J.A., Connerton, I., Cummings, N., Lo Leggio, L., Scott, M., Hazlewood, G.P., Laurie, J.I., Gilbert, H.J., Pickersgill, R.W. (1994) Structure 2: 1107
Crystallization and Preliminary X-Ray Analysis of the Catalytic Domain of Xylanase a from Pseudomonas Fluorescens Subspecies Cellulosa Pickersgill, R.W., Jenkins, J.A., Scott, M., Connerton, I., Hazlewood, G.P., Gilbert, H.J. (1993) J Mol Biol 229: 246
Organizational Affiliation:
Department of Protein Engineering, Institute of Food Research, Reading Laboratory, England.
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