Required for high affinity copper (probably reduced Cu I) transport into the cell (By similarity). Plays a role in fungal pathogenesis during host infection (PubMed:17290306, PubMed:23033470). Expression is highly induced by the CUF1 copper regulatory factor in response to copper deprivation and repressed in presence of physiologically low concentrations of copper (PubMed:15334556, PubMed:17290306). Expressed at high levels after phagocytosis by macrophage-like cells and during infection of mouse brains, but not lungs, consistent with limited copper availability during neurologic infection (PubMed:17290306). Exhibits a significant reduction in survival in macrophages after activation with gamma interferon (PubMed:23033470). The CTR4 copper-sensing promoter can be used to construct plasmids that offer efficient and regulated expression in C.neoformans (PubMed:15334556). Belongs to the copper transporter (Ctr) (TC 1.A.56) family. SLC31A subfamily.