The mkdom and XDOM programs have been used to analyze the domain organizations of the NBD proteins. The analysis revealed three types of organization in Streptococcus mutans: (1) the dimeric ATP-binding proteins (NBD-NBD) (e.g. SMu1757); (2) the membrane/ATP-binding domain associations (MSD-NBD)(e.g. Smu0258), and (3) the isolated NBD.

Red box: Walker A motif

Black box: signature and Walker B motif