Contains FMN. This enzyme oxidizes 2-oxazoline, 5-methyl-2-oxazoline, and 2-thiazoline within peptides, which were formed by EC 6.2.2.2, oxazoline synthase, and EC 6.2.2.3, thiazoline synthase, to the respective pyrrole-type rings. The enzyme is found as either a stand-alone protein or as a domain within a multifunctional protein (the G protein) that also functions as a peptidase.
The expected taxonomic range for this enzyme is: Bacteria, Eukaryota
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REACTION
REACTION DIAGRAM
COMMENTARY
ORGANISM
UNIPROT
LITERATURE
a [protein]-(1S,4R)-2-(C-substituted-aminomethyl)-4-acyl-2-thiazoline + O2 = a [protein]-(S)-2-(C-substituted-aminomethyl)-4-acyl-1,3-thiazole + H2O2
(1)
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-
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a [protein]-(S,S)-2-(C-substituted-aminomethyl)-4-acyl-2-oxazoline + O2 = a [protein]-(S)-2-(C-substituted-aminomethyl)-4-acyl-1,3-oxazole + H2O2
(2)
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-
-
a [protein]-(S,S)-2-(C-substituted-aminomethyl)-4-acyl-5-methyl-2-oxazoline + O2 = a [protein]-(S)-2-(C-substituted-aminomethyl)-4-acyl-5-methyl-1,3-oxazole + H2O2
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SYSTEMATIC NAME
IUBMB Comments
a [protein]-2-oxazoline:oxygen oxidoreductase (2-oxazole-forming)
Contains FMN. This enzyme oxidizes 2-oxazoline, 5-methyl-2-oxazoline, and 2-thiazoline within peptides, which were formed by EC 6.2.2.2, oxazoline synthase, and EC 6.2.2.3, thiazoline synthase, to the respective pyrrole-type rings. The enzyme is found as either a stand-alone protein or as a domain within a multifunctional protein (the G protein) that also functions as a peptidase.
Substrates: proposed general mechanism for McbC: an activated Tyr202 abstracts a proton from the A carbon of an azoline substrate, which results in E2 elimination of the antiproton from the B carbon and hydride transfer to FMN. Instead of a proton being provided to FMN by a general base to yield FMNH2, the negative charge on N1 of FMN may be stabilized by a salt bridge with Arg233 Products: -
each McbC subunit contributes to the binding of the FMN cofactor molecules, with Arg82 of one McbC subunit and Arg117 of the other forming salt bridges with the phosphate group and Arg181 interacting with the O2 of FMN
during biosynthesis of microcin B17, azole introduction into the microcin B17 precursor requires coordination of the activities of the heterocyclase, which converts Ser and Cys residues into azolines, and the dehydrogenase, which oxidizes the azolines to azoles
enzyme is part of microcin B17 synthase. The complex three proteins, McbB, McbC, and McbD, that convert 14 residues into the eight mono- and bisheterocyclic moieties in vitro that confer antibiotic activity on mature microcin B17 via a three-step sequence of cyclization, net dehydration, and subsequent two-electron dehydrogenation
the primary sequence of patellamides A and C is encoded on a single ORF that resembles a precursor peptide. This prepatellamide is heterocyclized to form thiazole and oxazoline rings, and the peptide is cleaved to yield the two cyclic patellamides, A and C
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CRYSTALLIZATION (Commentary)
ORGANISM
UNIPROT
LITERATURE
to 3.15 A resolution, space group P412121 with two molecules found in the asymmetric unit. The structure is composed of a novel domain and an FMN nitroreductase domain. The N-terminal domain contains a portion (residues 7-86) which possesses the same fold as the leader binding domain of TruD, the so-called peptide-clamp domain. The C-terminal domain (residues 323-469) contains the FMN molecule and has a high degree of homology to the putative nitroreductase from Anabaena variabilis
structures of synthetase McbBCD reveal an octameric B4C2D2 complex with two bound substrate peptides. Each McbB dimer clamps the N-terminal recognition sequence, while the C-terminal heterocycle of the modified peptide is trapped in the active site of McbC. The McbD and McbC active sites are distant from each other, which necessitates alternate shuttling of the peptide substrate between them, while remaining tethered to the McbB dimer
Structure of the cyanobactin oxidase ThcOx fromCyanothece sp. PCC 7425, the first structure to be solved at Diamond Light Source beamline I23 by means of S-SAD
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