Cuprous ions can disrupt the structure and functions of the RING finger domain of RNF11†
Copper is an essential element that plays crucial roles in a variety of biological processes, while excessive copper is harmful to cells. RNF11 is a RING finger protein associated with cell proliferation and development and metastasis of cancer cells. Here we find that cuprous ions can bind to the RING finger domain of RNF11 with a high binding affinity (disassociation constant 1.80 × 10−17 M). Cuprous ions are capable of depleting zinc ions from RNF11 and disrupting the structure and function of the protein. Circular dichroism and NMR measurements indicate that Cu(I) binding disrupts the secondary structures of RNF11 and further induces protein aggregation. NMR titration confirms that Cu(I) binds to the Zn(II) coordination residues. Consequently, cuprous binding interferes with the formation of RNF11/UBE2N complexes, a crucial step of the ubiquitination process. In addition, cellular assays confirmed that copper ions affect its function as a transcriptional regulator for SEC23B, SEC24B, and SEC24D. This result indicates that the alteration of copper homeostasis in cells could influence the RNF11-associated regulation processes.