PNNL

Abstract

The formation of the unique catalytic tetranuclear copper cluster (CuZ) of nitrous oxide reductase, N2OR, requires the coexpression of a multiprotein assembly apparatus encoded by the nosDFYL operon. NosL, one of the proteins encoded by this transcript, is a 20 kDa lipoprotein of the periplasm that has been shown to bind copper(I), although its function has yet to be detemined. Cu(I) EXAFS data collected on the holo protein demonstrated that features of the copper binding site are consistent with a role for this protein as a metallochaperone, a class of metal ion transporters involved in metal resistance, homeostasis, and metallocluster biosynthesis. To test this hypothesis and to gain insight into other potential functional roles for this protein in the N2OR system, the three-dimensional solution structure of apo NosL has been solved by solution NMR methods. The structure of apo NosL consists of two relatively independent homologous domains that adopt an unusual topology.