FIG 3.
VxrA-SD in VxrA-SD_2 structure and its comparison to VxrA-SD_1 structure. (A) A VxrA-SD dimer in VxrA-SD_2 structure, in which two VxrA-SD dimers form a dimer of dimer, a tetramer (not shown in the figure). (B) A side view of a VxrA-SD_2 dimer, presumably sitting on the membrane with its N and C termini connected to transmembrane helices. (C) A structural alignment of one of the VxrA-SD monomers (monomer A) from VxrA-SD dimers from VxrA-SD_1 and _2 structures, respectively. This figure shows that the main body of VxrA-SD is quite rigid without significant conformational change. However, when one monomer (monomer A) is aligned, the other monomer (monomer B) shows a large conformational change with a relative rotation of about 150 degrees. (D) The relative rotation is apparently associated with the rotation of β hairpin while the β-linker serves as the rotating henge. The flexibility of the β-linker makes a scissoring-like motion of two pairing VxrA-SDs (blades) possible.