Functional and structural characterization of Stenotrophomonas maltophilia EntB, an unusual form of isochorismatase for siderophore synthesis

Nas, M.Y.; Gabell, J.; Inniss, N.; Minasov, G.; Shuvalova, L.; Satchell, K.J.F.; Cianciotto, N.P.

doi:10.1107/S2053230X2500490X

Figure 3
Structure–sequence alignments of EntB homologs. (a) ESPript was used to generate an alignment of EntB homologs from S. maltophilia (Sm), P. aeruginosa (Pa), Streptomyces sp. ATCC 700974 (St), V. cholerae (Vc) and E. coli (Ec). The isochorismatase (ICL) and ArCP domains of the enzymes are marked below the sequences. The secondary-structural elements from SmEntB are depicted above the sequences. Inverted blue triangles mark residues of the hydrophobic pocket, inverted tan triangles mark those that interact with isochorismate (ISC) in the PaPhzD and VcVibB structures, and inverted gray triangles mark residues of the dimer interface that align across all homologs. An inverted tan triangle outlined in blue marks a single residue that is characterized as being part of the hydrophobic pocket and interacts with ISC, and an inverted gray triangle outlined in blue marks a residue that is predicted to interact with ISC and contribute to the dimer interface. (b) An overlay of a surface projection of SmEntB and PaPhzD–ISC depicting an enlarged view of the ISC binding pocket. Residues that are conserved in this pocket are depicted as lines with their carbon backbones colored lilac for SmEntB and gray for PaPhzD, N atoms in blue and O atoms in red. Residues are numbered according to the SmEntB structure. (c) An overlay of the SmEntB (lilac), PaPhzD (PDB entry 1nf8, gray) and VcVibB (salmon) structures depicted as transparent cartoons. An enlarged view of the active site is shown. ISC from PaPhzD (gray C atoms) and VcVibB (salmon C atoms) and a formate molecule (lilac C atoms) are shown. Residues that interact with ISC or formate and are conserved in all three structures are depicted as sticks, with N and O atoms colored as in (b). Water molecules identified in at least two of the active sites of the structure are shown as small spheres colored according to the carbon backbones. Dashed lines indicate hydrogen bonds and are colored according to the carbon backbones. Residues are numbered according to the SmEntB structure.

STRUCTURAL BIOLOGY
COMMUNICATIONS

ISSN: 2053-230X

Volume 81| Part 7| July 2025|

https://doi.org/10.1107/S2053230X2500490X

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