engleski

Bacterial single-stranded dna-binding proteins are phosphorylated on tyrosine

Single stranded DNA binding proteins (SSBs) are ubiquitous proteins that bind DNA in a sequence independent manner to maintain genome integrity in various stages of DNA metabolism such as replication, recombination and repair. Besides stabilizing single-stranded DNA (ssDNA), SSBs interact with enzymes such as DNA polymerase, RNA polymerase or DNA helicase thus modulating their activity. Although accomplishing similar functions, bacterial and eukaryotic SSBs differ considerably in their structure. It has been known that eukaryotic SSBs are regulated by phosphorylation on several serine and threonine residues, to our knowledge phosphorylation of SSBs in bacteria has not been reported. By immunoaffinity chromatography we identified Streptomyces griseus Ssb as a novel target of bacterial tyrosine kinase. Since genes encoding protein-tyrosine kinases have not been recognized in streptomycetes and SSBs from Streptomyces coelicolor and Bacillus subtilis share 40% identity, we used a B. subtilis protein-tyrosine kinase YwqD to phosphorylate two cognate SSBs (Ssb and YwpH) in vitro. We show that phosphorylation of B. subtilis Ssb increased binding to single-stranded DNA. Eukaryal SSBs are hyper-phosphorylated under DNA-damaging conditions. In contrast, B. subtilis Ssb phosphorylation is reduced by mitomycin-induced DNA damage. Tyrosine phosphorylation of heterologous B. subtilis and S. coelicolor SSBs, and homologous Escherichia coli Ssb occurred during their synthesis in E. coli, indicating that tyrosine phosphorylation of SSBs is a conserved process of post-translational modification in taxonomically distant bacteria.

bacterial single-strande

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