The X-ray crystal structure of a pseudoazurin from Sinorhizobium meliloti

The X-ray crystal structure of oxidised pseudoazurin from the denitrifying plant symbiotic bacterium Sinorhizobium meliloti (SmPAz2) has been solved to a resolution of 2.0 Å. The pseudoazurin from Sinorhizobium sp. is unusual as it forms an operon with a sulfite dehydrogenase enzyme, rather than a Cu nitrite reductase. Examination of the structure reveals that the geometric parameters of the Type I Cu site in SmPAz2 correlate with observed features in the electronic spectrum of the protein. Comparison of the structure of SmPAz2 with those of pseudoazurins from five other bacterial species shows that the surface of SmPAz2 bears a conserved hydrophobic patch encircled by positively-charged residues, which may serve as a recognition site for its redox partners.

Graphical abstractThe crystal structure of a pseudoazurin from Sinorhizobium meliloti, shows a typical pseudoazurin fold and a conserved electrostatic surface structure, indicating the possible site of its interaction with its redox partners.Figure optionsDownload full-size imageDownload as PowerPoint slide