Periplasmic localization of mutant variants of MotBC. (A) MotBC with single mutations or deletions. (B) MotBC with a T197I/R218W double mutation. Immunoblotting with the anti-MotB antibody of whole-cell proteins and periplasmic fractions of SJW1103 transformed with the wild type (WT), pNSK7; T197I, pNSK7(T197I); D198N, pNSK7(D198N); S215F, pNSK7(S215F); R218W, pNSK7(R218W); R223H, pNSK7(R223H); Δ197-210, pNSK7(Δ197-210); Δ211-226, pNSK7(Δ211-226); and T197I/R218W, pNSK7(T197I/R218W).