N-Terminal Domain of the Cu(I)-Binding Protein CusB

CusB is the membrane fusion protein of the Cu(I)/Ag(I) extrusion pump system CusCFBA in Escherichia coli. Although several crystal structures exist for the Cu(I)/Ag(I) binding protein CusB, its N-terminus region could never be characterized by spectroscopic techniques due to its intrinsic disorder. CusB N-terminus is of utmost importance as it facilitates the uptake of Cu(I) and Ag(I) ions from the periplasm and thus plays an essential role in survival of E. coli cells in media containing high concentrations of these ions. It was shown experimentally to chelate the metal nearly as well as the full-length CusB in in vivo studies on the survival of E. coli cells at elevated Cu(I) concentrations. Metal transfer was also shown to occur between the CusB N-terminus and the periplasmic metallochaperone of the CusCFBA system, CusF. Experimental and computational studies performed on this protein domain conclude that its observed structural disorder is only minimally impacted upon metal binding. Molecular dynamics simulations revealed some secondary structural motifs within the disorder and observed that complexation with CusF mostly relieves the observed disorder. 3D Structure Schematic representation of (a) apo and (b) Cu(I)-bound Cus-B N-terminus. Extracted from molecular dynamics simulations involving these models. Amino acid sequences were taken from the PDB structure 3NE5 but the structures were extracted from our MD simulations. Prepared with PyMOL.3 Keywords: binding protein; metal homeostasis; metal ion extrusion; metal ion extrusion pump; resistance-nodulation-division; membrane fusion protein; CusCFBA; CusCBA; copper; silver