 | Acta Crystallographica Section F Acta Crystallographica Section F STRUCTURAL BIOLOGY COMMUNICATIONS |
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![[Figure 2]](no5216fig2mag.jpg)
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Figure 2
Structural comparison of the substrate-binding sites of AtGABA-T and P. jessenii ω-aminotransferase (PjAT; PDB entry 6g4e). Key residues involved in substrate recognition and the PLP cofactor are shown as stick models. (a) Substrate-binding site of AtGABA-T near the PLP cofactor. Residues forming the substrate-binding pocket are shown, with Arg423 positioned as a putative anchor residue for substrate capture. (b) Substrate-binding site of PjAT in complex with the substrate analog 6-aminohexanoic acid (AHA). The external aldimine formed between AHA and PLP is shown. Arg417 of PjAT anchors the carboxylate group of AHA by forming a salt bridge. Dashed lines indicate the salt-bridge and hydrogen-bond interactions between Arg417 and AHA. (c) Superposition of the AtGABA-T and PjAT active sites. Trp91 and Arg423 of AtGABA-T, Ser87 and Arg417 of PjAT, and the PLP cofactor and PLP–AHA external aldimine are shown as stick models. The superposition highlights that Trp91 of AtGABA-T occupies a bulkier position than the corresponding serine residue of PjAT, suggesting that this steric difference may influence the local conformational environment of the anchoring arginine near the ligand-binding site. (d) Schematic model illustrating a possible rearrangement of the anchor residue in AtGABA-T [corresponding to (a)]. A two-dimensional schematic representation of the AtGABA-T substrate-binding site illustrates a possible spatial relationship between Arg423 and Trp91 (corresponding to Ser87 in PjAT). This model suggests that accommodation of GABA may require local conformational adjustment of Arg423 to allow salt-bridge formation with the substrate carboxylate. (e) Schematic model of the substrate-binding mode in PjAT. A two-dimensional representation of the PjAT active site [corresponding to (b)] illustrates the established binding mode, in which Arg417 stably anchors the carboxylate group of AHA and the surrounding residues define the substrate-access channel. |
![[Figure 2]](no5216fig2.jpg)
| STRUCTURAL BIOLOGY COMMUNICATIONS |
ISSN: 2053-230X
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