Structural basis for copper/silver binding by the Synechocystis Synechocystis metallochaperone CopM

摘要

Copper homeostasis integrates multiple processes from sensing to storage and efflux out of the cell. CopM is a cyanobacterial metallochaperone, the gene for which is located upstream of a two‐component system for copper resistance, but the molecular basis for copper recognition by this four‐helical bundle protein is unknown. Here, crystal structures of CopM in apo, copper‐bound and silver‐bound forms are reported. Monovalent copper/silver ions are buried within the bundle core; divalent copper ions are found on the surface of the bundle. The monovalent copper/silver‐binding site is constituted by two consecutive histidines and is conserved in a previously functionally unknown protein family. The structural analyses show two conformational states and suggest that flexibility in the first α‐helix is related to the metallochaperone function. These results also reveal functional diversity from a protein family with a simple four‐helical fold.