This family represents the N-terminal region of MukB, one of a group of bacterial proteins essential for the movement of nucleoids from mid-cell towards the cell quarters (i.e. chromosome partitioning). The structure of the N-terminal domain consists of an antiparallel six-stranded beta sheet surrounded by one helix on one side and by five helices on the other side [1]. It contains an exposed Walker A loop in an unexpected helix-loop-helix motif (in other proteins, Walker A motifs generally adopt a P loop conformation as part of a strand-loop-helix motif embedded in a conserved topology of alternating helices and (parallel) beta strands)[1].

1: Crystal structure of the N-terminal domain of MukB: a protein involved in chromosome partitioning. van den Ent F, Lockhart A, Kendrick-Jones J, Lowe J; Structure Fold Des 1999;7:1181-1187. PMID:10545328