An unprecedented insight into the catalytic mechanism of copper nitrite reductase from atomic-resolution and damage-free structures.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 33523860.
- Also identified by DOI 10.1126/sciadv.abd8523 and PMC identifier 7775769.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
Copper-containing nitrite reductases (CuNiRs), encoded by <i>nirK</i> gene, are found in all kingdoms of life with only 5% of CuNiR denitrifiers having two or more copies of <i>nirK</i> Recently, we have identified two copies of <i>nirK</i> genes in several α-proteobacteria of the order Rhizobiales including <i>Bradyrhizobium</i> sp. ORS 375, encoding a four-domain heme-CuNiR and the usual two-domain CuNiR (<i>Br</i> <sup>2D</sup>NiR). Compared with two of the best-studied two-domain CuNiRs represented by the blue (<i>Ax</i>NiR) and green (<i>Ac</i>NiR) subclasses, <i>Br</i> <sup>2D</sup>NiR, a blue CuNiR, shows a substantially lower catalytic efficiency despite a sequence identity of ~70%. Advanced synchrotron radiation and x-ray free-electron laser are used to obtain the most accurate (atomic resolution with unrestrained SHELX refinement) and damage-free (free from radiation-induced chemistry) structures, in as-isolated, substrate-bound, and product-bound states. This combination has shed light on the protonation states of essential catalytic residues, additional reaction intermediates, and how catalytic efficiency is modulated.