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Fig. 6 | BMC Microbiology

Fig. 6

From: Chitinolytic enzymes contribute to the pathogenicity of Aliivibrio salmonicida LFI1238 in the invasive phase of cold-water vibriosis

Fig. 6

X-ray crystal structure of the AsLPMO10B AA10 LPMO domain. (A) Domain architecture of AsLPMO10A and -B. Domain boundaries are indicated by amino acid sequence numbers. SP stands for signal peptide, and CBM refers to the carbohydrate binding domain family. (B) Cartoon representation of the crystal structure, with the topology assigned as described by Vaaje-Kolstad et al. [47]. The loop short (LS, purple), loop 2 (L2, red), loop 3 (L3, orange) and active site residues (yellow) are indicated by different colors and labeled. (C) Active site of AsLPMO10B, domain 1. The copper ion (bronze) is coordinated by the N-terminus, the side chain Nδ1 of His26 and the side chain Nε1 of His136, forming the so-called histidine brace motif (distance to copper indicated). In the AA10 family, a phenylalanine residue (Phe208) replaces the tyrosine residue found in many other LPMOs, which provides a loose axial coordination for the copper ion. Glu206 was refined in two alternative conformations. In other LPMOs, this residue is often replaced by a glutamine residue (Gln). (D) Conservation of aromatic amino acids among LPMOs, as revealed by substrate docking. Loop-2 Trp46 from AsLPMO10B (teal) is conserved in the viral LPMO fusolin (Trp20; green; PDB ID: 4YN2), a close structural homolog of AsLPMO10B. Their placement mirrors that of Tyr203 (orange), a substrate-binding residue found on the long C-terminal loop (LC) in Panus similis LPMO9A (PDB ID: 5ACI). LPMOs that carry both LC and L2 loops bear aromatic amino acids matching the positions of both Trp46 and Tyr203 (i.e. Tyr24 and Tyr212 on Thermoascus aurantiacus GH61 isozyme A, colored magenta PDB ID: 2YET). The structures of the three proteins were aligned by secondary structure matching (SSM)

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