Part of the ABC transporter complexes DasABC-MsiK and NgcEFG-MsiK involved in N,N'-diacetylchitobiose ((GlcNAc)2) uptake. Responsible for energy coupling to the transport system. The DasABC-MsiK complex is composed of two ATP-binding proteins (MsiK), two transmembrane proteins (DasB and DasC) and a solute-binding protein (DasA) (Probable). The NgcEFG-MsiK complex is composed of two ATP-binding proteins (MsiK), two transmembrane proteins (NgcF and NgcG) and a solute-binding protein (NgcE) (Probable). Constitutively expressed. Disruption of the gene severely affects the ability of the mutant to utilize maltose, cellobiose, starch, cellulose, chitin and chitosan, but not glucose. The null mutant lacks (GlcNAc)2-uptake activity, but GlcNAc transport activity is unaffected. Mutant shows defects in induction of chitinase production. Belongs to the ABC transporter superfamily.