Preparation of YidC27–266 and cysteine mutants of YidC27–266. (a) Construction of YidC27–266. The amino-acid sequences of the N- and C-terminal regions of YidC are shown. A His8 tag followed by the Tobacco etch virus (TEV) protease cleavage site were introduced at the 26th position. The C-terminal 14 residues were removed. (b) Methylmercury chloride labelling of wild-type YidC27–266 and cysteine mutants of YidC27–266. The tetramethylrhodamine-5-maleimide (TMRM) signals (top) and the gel stained with SimplyBlue SafeStain (bottom).