C59S |
mutantion renders enzyme maturation sensitive to molybdenum cofactor availability. Residue C59 is a ligand to the FS0 [4Fe-4S] cluster. In the presence of trace amounts of molybdate, the C59S variant assembles normally to the cytoplasmic membrane and supports respiratory growth on DMSO, although the ground state of FS0 as determined by EPR is converted from high-spin, S = 3/2, to low-spin, S = 1/2. In the presence of the molybdenum antagonist tungstate, wild-type enzyme lacks molybdo-bis(pyranopterin guanine dinucleotide), but is translocated via the Tat translocon and assembles on the periplasmic side of the membrane as an apoenzyme. The C59S variant cannot overcome the dual insults of amino acid substitution plus lack of molybdo-bis(pyranopterin guanine dinucleotide) , leading to degradation of the DmsABC subunits |
Escherichia coli |