9uba
The structure of the AglA_K196R-Arg complex
Structural highlights
Publication Abstract from PubMedThe YqcI/YcgG family of heme-dependent enzymes catalyzes guanidine N-H hydroxylation, a critical yet enigmatic step in bioactive natural product biosynthesis. Here, this mechanistic puzzle is resolved through high-resolution structural snapshots of AglA, a prototypical YqcI/YcgG member, revealing a non-canonical heme-binding "sandwich" fold. A dynamic regiochemical gating mechanism is uncovered: substrate-induced remodeling of loop L2 and key residues (Phe152, Arg179, Phe182) spatially constrains the guanidine group of aminomethylphosphonate-linked arginine (AMPn-Arg), enforcing exclusive internal N(epsilon) hydroxylation. Single-site mutations rewire hydrogen-bond networks to enable hydroxylation of free L-arginine with controllable regioselectivity (internal N(delta) vs terminal N(omega)) while preserving native internal N(epsilon) selectivity for AMPn-Arg. Crystal structures of engineered variants with free arginine, together with MD simulations, explain how subtle rearrangements of loop L2 and residues Phe152/Arg179/Phe182 pivot the guanidinium group relative to the heme Fe(IV) = O intermediate. Fusing AglA to its native PDR/VanB reductase yields a self-sufficient chimera with improved catalytic efficiency. This work establishes a structural blueprint for tuning guanidino N-H hydroxylation and demonstrates proof-of-principle control of regioselectivity in a non-canonical heme enzyme, thereby advancing the synthesis of arginine-based antibiotics and precision-functionalized therapeutics. A Dynamic Gate Enables Regioselective Hydroxylation of Free Arginine by a Non-Canonical Heme Enzyme.,Sun Y, Dou C, Yan W, Chen P, Zhang L, Zhou D, Zheng Y, Long Z, Li S, Xu X, Huang Q, Zhu X, Cheng W Adv Sci (Weinh). 2025 Nov 12:e13032. doi: 10.1002/advs.202513032. PMID:41221789[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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