Part of the high-affinity ABC transporter complex ZnuABC involved in zinc import (Probable). Responsible for the translocation of the substrate across the membrane (By similarity). ZnuABC-mediated zinc transport is required for comF expression and competence development. The complex is composed of two ATP-binding proteins (ZnuC), two transmembrane proteins (ZnuB) and a solute-binding protein (ZnuA). Repressed by zinc via the metallo-regulatory protein Zur. Disruption results in low transformability. Belongs to the ABC-3 integral membrane protein family.