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Publication Abstract from PubMed

Flavodoxins are small proteins that shuttle electrons in a range of reactions in microorganisms. Flavodoxins contain a redox-active cofactor, a flavin mononucleotide (FMN), and it is well established that when flavodoxins are reduced by one electron, a peptide bond close to the FMN isoalloxazine ring flips to form a new hydrogen bond with the FMN N5H, stabilising the one-electron reduced state. Here we present high-resolution crystal structures of Flavodoxin 1 from Bacillus cereus in both the oxidised (ox) and one-electron reduced (semiquinone, sq) state. We observe a mixture of conformers in the oxidised state; a 50:50 distribution between the established oxidised conformation where the peptide bond is pointing away from the flavin, and a conformation where the peptide bond is pointing towards the flavin, approximating the conformation in the semiquinone state. We use single-crystal spectroscopy to demonstrate that the mixture of conformers is not caused by radiation damage to the crystal. This is the first time that such a mixture of conformers is reported in a wild-type flavodoxin. We therefore carried out a survey of published flavodoxin structures, which shows that several proteins have a pronounced conformational flexibility of this peptide bond. The degree of flexibility seem to be modulated by the presence, or absence, of stabilising interactions between the peptide bond carbonyl and its surrounding amino acids. We hypothesise that the degree of conformational flexibility will affect the flavodoxin ox/sq redox potential. This article is protected by copyright. All rights reserved.

High-resolution crystal structures reveal a mixture of conformers of the Gly61-Asp62 peptide bond in an oxidised flavodoxin from Bacillus cereus.,Gudim I, Lofstad M, van Beek W, Hersleth HP Protein Sci. 2018 May 3. doi: 10.1002/pro.3436. PMID:29722453^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.