Mutagenesis of cysteine residues in dptC from Salmonella enteric serovar Cerro 87 and its effects on DNA phosphorothioate modification

Abstract:

Abstract:［Objective］DNA phosphorothioate modification (DNA sulfur modification，a non-bridging oxygen swapped with a sulfur) exists in diverse bacteria． Salmonella enterica serovar Cerro 87 is one of the bacteria that harbor the DNA sulfur modification． The modification is carried out by the products of a four-membered gene cluster，dptBCDE．Transformation of Escherichia coli DH10B with the dptBCDE gene cluster endows the strain with DNA sulfur modification capability． Deletion of dptC abolished the modification． Here，we studied the function of dptC in DNA sulfur modification．［Methods］Six cysteine residues in dptC were mutated individually within the dptBCDE gene cluster． Mutants were then tested for DNA sulfur modification．［Results］Among the 6 cysteine mutations (C39，C146，C262，C273，C280，and C283)，5 abolished DNA modification except for C39，suggesting that C146，C262，C273，C280，and C283 are essential for DNA sulfur modification． Sequence alignment shows that these five cysteine residues are conserved among different strains．［Conclusion］Mutation at anyone of C146，C262，C273，C280 and C283 of dptC abolished DNA modification．Our results shed light on further study of DNA sulfur modification biochemical pathway．