Middle Components (MCs) of the ABC-3C biological conflict systems occupy the central position between the catalytic effector and ABC ATPases of the systems. MCs are defined by distinctive patterns of conserved charged residues. As some MCs are HTH domains, they are predicted to function akin to kleisins as DNA-binding partners for the ABC ATPases, assisting in recognition and responding to invasive elements such as DNA viruses. MC8 is a MC unifiable with the HTH fold [1].

1: Comprehensive classification of ABC ATPases and their functional radiation in nucleoprotein dynamics and biological conflict systems. Krishnan A, Burroughs AM, Iyer LM, Aravind L; Nucleic Acids Res. 2020;48:10045-10075. PMID:32894288