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Biochim Biophys Acta Bioenerg. 2017 Feb;1858(2):95-102. doi: 10.1016/j.bbabio.2016.11.008. Epub 2016 Nov 15.

The flavinyl transferase ApbE of Pseudomonas stutzeri matures the NosR protein required for nitrous oxide reduction.

Author information

1
Institute for Biochemistry, Albert-Ludwigs-Universität Freiburg, 79104 Freiburg im Breisgau, Germany.
2
Institute for Biochemistry, Albert-Ludwigs-Universität Freiburg, 79104 Freiburg im Breisgau, Germany; BIOSS Centre for Biological Signalling Studies, Schänzlestrasse 1, 79104 Freiburg im Breisgau, Germany.
3
Institute for Biochemistry, Albert-Ludwigs-Universität Freiburg, 79104 Freiburg im Breisgau, Germany; BIOSS Centre for Biological Signalling Studies, Schänzlestrasse 1, 79104 Freiburg im Breisgau, Germany. Electronic address: einsle@biochemie.uni-freiburg.de.

Abstract

The copper-containing enzyme nitrous oxide reductase (N2OR) catalyzes the transformation of nitrous oxide (N2O) to dinitrogen (N2) in microbial denitrification. Several accessory factors are essential for assembling the two copper sites CuA and CuZ, and for maintaining the activity. In particular, the deletion of either the transmembrane iron-sulfur flavoprotein NosR or the periplasmic protein NosX, a member of the ApbE family, abolishes N2O respiration. Here we demonstrate through biochemical and structural studies that the ApbE protein from Pseudomonas stutzeri, where the nosX gene is absent, is a monomeric FAD-binding protein that can serve as the flavin donor for NosR maturation via covalent flavinylation of a threonine residue. The flavin transfer reaction proceeds both in vivo and in vitro to generate post-translationally modified NosR with covalently bound FMN. Only FAD can act as substrate and the reaction requires a divalent cation, preferably Mg2+ that was also present in the crystal structure. In addition, the reaction is species-specific to a certain extent.

KEYWORDS:

ApbE/NosX family protein; Bacterial denitrification; Flavin binding protein; Nitrous oxide reductase; X-ray crystallography

PMID:
27864152
DOI:
10.1016/j.bbabio.2016.11.008
[Indexed for MEDLINE]
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