FIG. 1.

Multicopy effect of MotB_C on the motility of wild-type cells. (A) Primary structures of the Salmonella MotB protein and an N-terminally truncated fragment missing the N-terminal 77 residues, MotB_C. MotB has a single transmembrane domain (black) in the N-terminal region and a putative PGB motif (gray) in the large periplasmic domain. Plasmid pNSK7 encodes the MotB_C fragment (residue 78 to C-terminal position 309) fused to a PelB leader sequence (PelB_L, 22 amino acids, hatched) and a His₆ tag at its N and C termini, respectively. Plasmid pNSK8 does not contain PelB_L at the N terminus. (B) Periplasmic localization of the MotB_C-His₆ fragment. Immunoblotting with the polyclonal anti-MotB antibody of whole-cell proteins (whole cell) and periplasmic fractions (periplasm) prepared from SJW1103 transformed with pTrc99A (vector control), pNSK8, or pNSK7. (C) Swarming motility assay of SJW1103 carrying pTrc99A, pNSK8, or pNSK7 on soft-agar plates with or without 1 mM IPTG. Plates were incubated at 30°C for 6 h.