The Copper Chaperone NosL Forms a Heterometal Site for Cu Delivery to Nitrous Oxide Reductase

The final step of denitrification is the reduction of nitrous oxide (N2O) to N-2, mediated by Cu-dependent nitrous oxide reductase (N2OR). Its metal centers, Cu-A and Cu-Z, are assembled through sequential provision of twelve Cu-I ions by a metallochaperone that forms part of a nos gene cluster encoding the enzyme and its accessory factors. The chaperone is the nosL gene product, an 18 kDa lipoprotein predicted to reside in the outer membrane of Gram-negative bacteria. In order to better understand the assembly of N2OR, we have produced NosL from Shewanella denitrificans and determined the structure of the metal-loaded chaperone by X-ray crystallography. The protein assembled a heterodinuclear metal site consisting of Zn-II and Cu-I, as evidenced by anomalous X-ray scattering. While only Cu-I is delivered to the enzyme, the stabilizing presence of Zn-II is essential for the functionality and structural integrity of the chaperone.

Automated summary

The final step of denitrification involves the reduction of nitrous oxide to N-2 by Cu-dependent nitrous oxide reductase (N2OR). The assembly of N2OR is mediated by a metallochaperone encoded by the nos gene cluster, with Cu-A and Cu-Z metal centers. While only Cu-I is delivered to the enzyme, the presence of Zn-II is crucial for the functionality and structural integrity of the chaperone.