This family includes BREX protein BrxB from Bacillus cereus, which is part of a type 1 BREX (bacteriophage exclusion) system, a system that provides immunity against bacteriophage, which allows phage adsorption but prevents phage DNA replication, without degradation of the phage DNA [1]. The exact function of BrxB is not clear.

1: BREX is a novel phage resistance system widespread in microbial genomes. Goldfarb T, Sberro H, Weinstock E, Cohen O, Doron S, Charpak-Amikam Y, Afik S, Ofir G, Sorek R; EMBO J. 2015;34:169-183. PMID:25452498