Part of the energy-coupling factor (ECF) transporter complex CbiMNOQ involved in cobalt import. The complex confers cobalt uptake upon expression in E.coli; can also transport nickel with a very low affinity. Presumably responsible for energy coupling to the transport system. Cofactor biosynthesis; adenosylcobalamin biosynthesis. Forms an energy-coupling factor (ECF) transporter complex composed of an ATP-binding protein (A component, CbiO), a transmembrane protein (T component, CbiQ) and 2 possible substrate-capture proteins (S components, CbiM and CbiN) of unknown stoichimetry. Subcomplexes composed of CbiMQO can be isolated from membranes but the CbiN subunit is not isolated in association with them, suggesting it is only loosely associated. Expression of just CbiMN in E.coli confers some cobalt uptake. Belongs to the ABC transporter superfamily.