SPECIFIC THIOL COMPOUNDS COMPLEMENT DEFICIENCY IN C-TYPE CYTOCHROME BIOGENESIS IN ESCHERICHIA-COLI CARRYING A MUTATION IN A MEMBRANE-BOUND DISULFIDE ISOMERASE-LIKE PROTEIN

Escherichia coli JCB606 carries a mutation in the dipZ gene, known to code for a disulphide isomerase-like protein, with the consequence tha t hole forms of neither exogenous nor endogenous c-type cytochromes ar e synthesised. This failure has been overcome by adding compounds cont aining thiol groups to the growth medium. Only L-cysteine and 2-mercap toethane sulphonic acid were effective, suggesting a (stereo)specific binding site that could be occupied by these compounds in the absence of the catalytic domain of DipZ.