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Figure 2
RpNiR mutation sites and specific activity of the mutants. (A) The structure of wtRpNiR is shown as a cartoon with its monomers in different colours: slate, blue and grey. The details of key residues involved in the ET transfer between the cyt c domain and the CuNiR core domain are shown. The variants in this study including Ser321Met, Met148Leu, Gln262Asn and Phe295Leu are labelled in red. The water molecules associated with each channel are shown as spheres with the respective colour, otherwise they are shown as red spheres. The copper-coloured spheres are T1Cu, deep blue spheres are T2Cu, the black dashed lines represent hydrogen bonds, yellow dashed lines represent through-bond interactions and red dashed lines represent the interactions involving copper sites. (B) The putative roles of mutated residues are described. (C) The specific activity of RpNiR mutants, including Ser321Met, Met148Leu, Phe295Leu and Gln262Asn, compared with wtRpNiR. Bars represent the mean; error bars indicate the standard deviation of three technical replicates (n = 3). pH activity profiles of wtRpNiR and mutants Ser321Met, Met148Leu, Phe295Leu and Gln262Asn are given in Fig. S1.

IUCrJ
Volume 13| Part 4| July 2026|
ISSN: 2052-2525
https://doi.org/10.1107/S2052252526004549