6R6M

Kusta0087/Kusta0088 Complex purified from Kuenenia stuttgartiensis

Summary for 6R6M

• Entry DOI: 10.2210/pdb6r6m/pdb
• Descriptor: Small soluble cyt c, Kusta0088, HEME C, ... (4 entities in total)
• Functional Keywords: heme-c, cystein ligation, electron transport
• Biological source: Kuenenia stuttgartiensis; More
• Total number of polymer chains: 2
• Total formula weight: 24430.27

Authors

Akram, M.,Barends, T. (deposition date: 2019-03-27, release date: 2019-10-02, Last modification date: 2024-11-20)

Primary citation

Akram, M.,Reimann, J.,Dietl, A.,Menzel, A.,Versantvoort, W.,Kartal, B.,Jetten, M.S.M.,Barends, T.R.M.
A nitric oxide-binding heterodimeric cytochromeccomplex from the anammox bacteriumKuenenia stuttgartiensisbinds to hydrazine synthase.
J.Biol.Chem., 294:16712-16728, 2019

PubMed Abstract: Anaerobic ammonium oxidation (anammox) is a microbial process responsible for significant nitrogen loss from the oceans and other ecosystems. The redox reactions at the heart of anammox are catalyzed by large multiheme enzyme complexes that rely on small cytochrome proteins for electron shuttling. Among the most highly abundant of these cytochromes is a unique heterodimeric complex composed of class I and class II -type cytochromes called NaxLS, which has distinctive biochemical and spectroscopic properties. Here, we present the 1.7 Å resolution crystal structure of this complex from the anammox organism (KsNaxLS). The structure reveals that the heme irons in each subunit exhibit a rare His/Cys ligation, which, as we show by substitution, causes the observed unusual spectral properties. Unlike its individual subunits, the KsNaxLS complex binds nitric oxide (NO) only at the distal heme side, forming 6cNO adducts. This is likely due to steric immobilization of the proximal heme-binding motifs upon complex formation, a finding that may be of functional relevance, because NO is an intermediate in the central anammox metabolism. Pulldown experiments with cell-free extract showed that the KsNaxLS complex binds specifically to one of the central anammox enzyme complexes, hydrazine synthase, which uses NO as one of its substrates. It is therefore possible that the KsNaxLS complex plays a role in binding the volatile NO to retain it in the cell for transfer to hydrazine synthase. Alternatively, we propose that KsNaxLS may shuttle electrons to this enzyme complex.

PubMed: 31548310
DOI: 10.1074/jbc.RA119.008788

Experimental method

X-RAY DIFFRACTION (1.7 Å)