title: The flavinyl transferase ApbE of Pseudomonas stutzeri matures the NosR protein required for nitrous oxide reduction.
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 CuAand 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.
authors.affiliation: Institute for Biochemistry, Albert-Ludwigs-Universität Freiburg, 79104 Freiburg im Breisgau, Germany.
authors.forename: Lin
authors.initials: L
authors.lastname: Zhang
authors.affiliation: Institute for Biochemistry, Albert-Ludwigs-Universität Freiburg, 79104 Freiburg im Breisgau, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Trncik
authors.affiliation: 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.
authors.forename: Susana L A
authors.initials: SLA
authors.lastname: Andrade
authors.affiliation: 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.
authors.forename: Oliver
authors.initials: O
authors.lastname: Einsle
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism*; D002384:Catalysis; D003300:Copper / Q000378:metabolism; D005415:Flavins / Q000378:metabolism*; D005420:Flavoproteins / Q000378:metabolism*; D008274:Magnesium / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism; D009609:Nitrous Oxide / Q000378:metabolism*; D010088:Oxidoreductases / Q000378:metabolism*; D011499:Protein Processing, Post-Translational / Q000502:physiology; D044223:Pseudomonas stutzeri / Q000378:metabolism*; D014166:Transferases / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D005415:Flavins; D005420:Flavoproteins; D008565:Membrane Proteins; D003300:Copper; D010088:Oxidoreductases; C022763:nitrous oxide reductase; D014166:Transferases; D008274:Magnesium; D009609:Nitrous Oxide
keywords: ApbE/NosX family protein; Bacterial denitrification; Flavin binding protein; Nitrous oxide reductase; X-ray crystallography