8dsn
Peptidylglycine alpha hydroxylating monoxygenase, Q272A
Structural highlights
FunctionAMD_RAT Bifunctional enzyme that catalyzes 2 sequential steps in C-terminal alpha-amidation of peptides. The monooxygenase part produces an unstable peptidyl(2-hydroxyglycine) intermediate that is dismutated to glyoxylate and the corresponding desglycine peptide amide by the lyase part. C-terminal amidation of peptides such as neuropeptides is essential for full biological activity. Publication Abstract from PubMedPeptidylglycine monooxygenase (PHM) is essential for the biosynthesis of many neuroendocrine peptides via a copper-dependent hydroxylation of a glycine-extended pro-peptide. The "canonical" mechanism requires the transfer of two electrons from one mononuclear copper (CuH, H-site) to a second mononuclear copper (CuM, M-site) which is the site of oxygen binding and catalysis. In most crystal structures the copper centers are separated by 11 A of disordered solvent, but recent work has established that a PHM variant H108A forms a closed conformer in the presence of citrate with a reduced Cu-Cu site separation of ~4 A. Here we report three new PHM structures where the H and M sites are separated by a longer distance of ~14 A. Variation in Cu-Cu distance is the result of a rotation of the M subdomain about a hinge point centered on the pro(199) -leu(200) -ile(201) triad which forms the linker between subdomains. The energetic cost of domain dynamics is likely small enough to allow free rotation of the subdomains relative to each other, adding credence to recent suggestions that an open-to-closed transition to form a binuclear oxygen binding intermediate is an essential element of catalysis. This inference would explain many experimental observations that are inconsistent with the current canonical mechanism including substrate-induced oxygen activation and isotope scrambling during the peroxide shunt. New structures reveal flexible dynamics between the subdomains of peptidylglycine monooxygenase. Implications for an open to closed mechanism.,Arias RJ, Welch EF, Blackburn NJ Protein Sci. 2023 Apr;32(4):e4615. doi: 10.1002/pro.4615. PMID:36880254[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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