9.B.276.  The Ciliate 9 TMS Membrane Protein (C9MP) Family 

Nothing is known about the functions of the N-terminal hydrophobic domains of these proteins other than they have about 9 TMSs followed by a large hydrophilic domain. Homologues of the N-terminal transmembrane domain are found only in ciliates. However, the C-terminal hydrophilic domain is universal.  It is a chromosomal segregation ATPase, Smc (Structural maintenance of chromosomes), that binds DNA throughout much of all of the cell cycle.  The SMC (Rabaptin; neuromodulin) family includes condensin and cohesin, which structure chromosomes to enable mitosis and long-range gene regulation. The mechanism of loop formation and the implications for how these complexes ultimately shape chromosomes have been discussed (van Ruiten and Rowland 2018). 

This family belongs to the .



van Ruiten, M.S. and B.D. Rowland. (2018). SMC Complexes: Universal DNA Looping Machines with Distinct Regulators. Trends Genet. [Epub: Ahead of Print]


TC#NameOrganismal TypeExample

XkR8 homologue of 913 aas and 8 - 10 N-terminal TMSs.  The C-terminal domain may be an ATPase involved in DNA repair/replication.


XkR8 homologue of Tetahymena thermophila


XkR8 homologue of 739 aas and 10 TMSs.


XkR8 homologue of Ichthyophthirius multifiliis