Fig. 1.

mxiH cysteine point mutants have normal secretion characteristics and form morphologically normal needles. (A) Exponential leakage of the Ipa proteins and (B) induced secretion of Ipa proteins after the addition (+) or not (−) of Congo red (Cr) were analysed by silver staining after SDS–PAGE. The positions of the major Ipa proteins detected by silver staining are indicated on the left side. (C and D) Electron micrographs of purified superlong MxiH_L32C and MxiH_V68C needles, negatively stained. Bar equals 20 nm. The data shown here are representative of two independent experiments giving similar results.