FIG 8.

MBP-ToxT N106F mutant is insensitive to the negative effector virstatin. (Top) V. cholerae O395 ΔtoxT mutant with plasmid-borne WT or mutant MBP-ToxT in dimethyl sulfoxide (DMSO) alone or 50 μM virstatin dissolved in DMSO. β-Galactosidase activity produced from chromosomal tcpA::lacZ in classical strain O395 ΔtoxT was measured. Statistical significance of ToxT mutant activation of tcpA::lacZ under each condition compared to WT ToxT activation of tcpA::lacZ under the same condition was calculated using Student's t test. Statistical significance of activation by a ToxT mutant without or with effector is denoted by an asterisk or plus sign, respectively (* or +, P < 0.05). (Bottom) Mean fold decrease in activation of tcpA::lacZ upon the addition of virstatin is shown for each ToxT mutant. Statistical significance of fold change for an MBP-ToxT mutant compared to fold change for WT MBP-ToxT was determined by Student's t test (*, P < 0.05); the dashed line represents fold change for WT ToxT with the addition of effector. ToxT mutants with results above the line had increased sensitivity to effector, while results below the line represent decreased sensitivity to effector. Error bars represent ± SEM.