Centromere Protein B (CENP-B) is a DNA-binding protein localized to the centromere. Within the N-terminal 125 residues, there is a DNA-binding region, which binds to a corresponding 17bp CENP-B box sequence. CENP-B dimers either bind two separate DNA molecules or alternatively, they may bind two CENP-B boxes on one DNA molecule, with the intervening stretch of DNA forming a loop structure. The CENP-B DNA-binding domain consists of two repeating domains, RP1 and RP2. This family corresponds to RP1 has been shown to consist of four helices in a helix-turn-helix structure.