1. Volume 2, Issue 11, Pages 1107-1116 (November 1994)
Structure of the catalytic core of the family F xylanase from Pseudomonas fluorescens and identification of the xylopentaose-binding sites 
Gillian W Harris, John A Jenkins, Ian Connerton, Nicola Cummings, Leila Lo Leggio, Mandy Scott, Geoffrey P Hazlewood, Judith I Laurie, Harry J Gilbert, Richard W Pickersgill 
Structure 
Volume 2, Issue 11, Pages (November 1994)
DOI: /S (94)00112-X

2. Figure 1
The eight-fold α/β-barrel architecture of the catalytic domain of xylanase A from P. fluorescens subsp. cellulosa drawn using MOLSCRIPT [33]. The eight β-strands are shown as arrows in red and the eight α-helices are shown in green. An additional α-helix is shown in yellow. Ca2+ binding stabilizes the loop after strand 7 and the substrate-binding subsites are formed by loops after strands 4–7. The substrate is shown using solid bonds. The active site nucleophile (Glu246) resides on strand 7 and the acid- base catalyst (Glu127) on strand 4. (b) Stereo Cα plot of the catalytic domain of xylanase A.
Structure 1994 2, DOI: ( /S (94)00112-X)

3. Figure 1
The eight-fold α/β-barrel architecture of the catalytic domain of xylanase A from P. fluorescens subsp. cellulosa drawn using MOLSCRIPT [33]. The eight β-strands are shown as arrows in red and the eight α-helices are shown in green. An additional α-helix is shown in yellow. Ca2+ binding stabilizes the loop after strand 7 and the substrate-binding subsites are formed by loops after strands 4–7. The substrate is shown using solid bonds. The active site nucleophile (Glu246) resides on strand 7 and the acid- base catalyst (Glu127) on strand 4. (b) Stereo Cα plot of the catalytic domain of xylanase A.
Structure 1994 2, DOI: ( /S (94)00112-X)

4. Figure 2
Sequence alignment of family F xylanases. The secondary structure (B indicates β-strand and H indicates α-helix) of xylanase A of P. fluorescens (PSEFL) is presented together with its sequence alignment with the following six family F enzymes (accession numbers, GENBANK or SWISSPROT, in parantheses): CLOTM, XynZ of Clostridium thermocellum (P10478); CELFI, endoglucanase precursor of C. fimi (P07986); ASPAK, XynA of Aspergillus awamori (P33559); STRLI, XynA of Streptomyces lividans (P26514); PENCH, 1,3-β-xylosidase of Penicillium chrysogenum (JN0575); FILFF, XynA of Filobasidium floriforme (JS0734). Residues conserved among these closely related family F sequences are indicated by bold type. The six carboxylates and the two histidines conserved throughout the family F sequences are indicated by asterisks.
Structure 1994 2, DOI: ( /S (94)00112-X)

5. Figure 3
Reaction mechanism for a retaining endo-β-1,4-xylanase. R is a number of xylose residues, HA is the acid catalyst. The structures in brackets are possible intermediates and R1 is hydrogen or a number of xylose residues. Intermediate (a) has the nucleophile stabilizing the oxo-carbonium ion, whereas in (b) the covalent intermediate is formed. Either of these intermediates could react with water and be hydrolyzed or react with another xylo-oligosaccharide to produce trans-glycosylation products.
Structure 1994 2, DOI: ( /S (94)00112-X)

6. Figure 4
The active site of xylanase A, indicating the positions and environments of glutamates 127 and 246 on b-strands 4 and 7. Histidines 79 and 215 close to Glu246, and Gln213 which forms a hydrogen bond with Glu127, are shown (see also Figure 5b and Figure7).
Structure 1994 2, DOI: ( /S (94)00112-X)

7. Figure 5
Residue 246 in the E246C and native xylanase A structures. (a) E246C structure and corresponding electron-density map at 2.5 Å resolution, with crystallographic R-factor of 0.20 showing cysteine 246. Nδ1 of His215 hydrogen bonds to Oδ1 of Asp248 and Nϵ2 hydrogen bonds to a water molecular. (b) The native structure and electron-density map at 3.0 Å with crystallographic R-factor of Nϵ2 of His215 hydrogen bonds Oϵ1 of Glu246. Both maps are contoured at 1σ.
Structure 1994 2, DOI: ( /S (94)00112-X)

8. Figure 5
Residue 246 in the E246C and native xylanase A structures. (a) E246C structure and corresponding electron-density map at 2.5 Å resolution, with crystallographic R-factor of 0.20 showing cysteine 246. Nδ1 of His215 hydrogen bonds to Oδ1 of Asp248 and Nϵ2 hydrogen bonds to a water molecular. (b) The native structure and electron-density map at 3.0 Å with crystallographic R-factor of Nϵ2 of His215 hydrogen bonds Oϵ1 of Glu246. Both maps are contoured at 1σ.
Structure 1994 2, DOI: ( /S (94)00112-X)

9. Figure 6
Side view of the β-barrel with surrounding α-helices, showing the long loops after strands 4 (left) and 7 (right) and shorter loops after strands 5 and 6 that form the substrate-binding cleft of xylanase A. Xylopentaose is shown bound to the active site. This figure was prepared using MOLSCRIPT [33].
Structure 1994 2, DOI: ( /S (94)00112-X)

10. Figure 7
Stereoview of the difference map showing xylopentaose, its density in the 4.0 Å difference map and the struct ure of xylanase A. The xylopentaose-binding subsites A–E are formed by the following residues: site A, Tyr220 and Asn253; site B, Glu185, Met217 and Tyr255; site C, Asn182, Asp131 and Arg250; site D, Asp134, Phe181, His215, Glu246, and Trp313 ; and site E, His79, Trp83, Glu127, Gln213, Trp305 and Trp313. Residues con served across the family F enzymes are shown in bold. Italicized residues are conservative substi tu tions.The electron density is consistent with cleavage of the β-1,4-glycosidic bond between subsites D and E, with Glu127 acting as the active-site acid-base and Glu246 as the nucleophile.
Structure 1994 2, DOI: ( /S (94)00112-X)

11. Figure 8
Stereoview of the Ca2+-binding loop of the E246C xylanase A structure. Ca2+ is shown as the yellow cross and water 347 as the red cross. The Ca2+ ligands are given in Table 1.
Structure 1994 2, DOI: ( /S (94)00112-X)

12. Figure 9
The averaged 3.0 Å electron-density map, in the region of β-strand 5 showing the quality of the map and the density for aromatics which were used to initially align the sequence with the electron-density map. The map is contoured at 1σ.
Structure 1994 2, DOI: ( /S (94)00112-X)