Figure 2: Comparison of EzrA with spectrin family proteins.
From: Structure and function of a spectrin-like regulator of bacterial cytokinesis
(a) Structure of the spectrin protein α-actinin (PDB 1HCI), with alternating triple helical bundle spectrin repeats coloured red and blue. (b) Superimposition of spectrin units from BsEzrA22–562 or SaEzrA24–214 (coloured red, yellow, green and blue, as in Fig. 1a) onto representative spectrin units coloured cyan from erythroid spectrin (top; PDB 3KBT), α-actinin (middle; PDB 1HCI) and brain spectrin (bottom; PDB 1U5P). (c) The angle between spectrin repeats 1 and 2 in BsEzrA22–562 is 37° and in SaEzrA24–214 it is 34°; the angle is also 37° between erythrocytic β-spectrin repeats 14 and 15 (PDB 3EDU). (d) Top—Orthogonal views of the relative positioning and different connectivity of the three α-helices in EzrA spectrin repeat 1 (residues 24–129) and in the fourth repeat (residues 630–745) of the rod domain of α-actinin (PDB 1HCI). The N-terminal helix in the bundle (a) is coloured blue, the middle helix (b) yellow and the C-terminal helix (c) red. Bottom—Schematic illustration of the different connectivity in the EzrA and spectrin three-helix bundles, viewed along the helix axes. An up arrow (helix a, c) represents an ‘up’ helix viewed along the helix axis in an N–C direction (N-terminus of helix axis above plane of page). A down arrow represents a ‘down’ helix viewed in the opposite direction.
