engleski

Tyrosine kinases in prokaryotic organisms and SSB proteins

In all organisms protein phosphorylation plays essential role in regulation of cellular processes. Until recently, tyrosine phosphorylation has been considered to be largely involved in eucaryotic signalling pathways. However, in bacteria data on this protein modification are accumulating during last decade. Our recent publication on tyrosine phosphorylation of single stranded DNA binding proteins (SSBs) in bacteria indicated that post-translational modification is conserved process in taxonomically distant bacteria. The aim of this study was to examine: tyrosine phosphorylation in cell-free extracts from different stages of Streptomyces growth ; (2) to compare phosphorylation of SSB protein from exponentially to late stationery phase and how (if) this modification varies with respect to tyrosine phosphorylation pattern, (3) to corelate A-factor (signalling molecule) cascade and tyrosine phosphorylation pattern in S.griseus strains (wild type and A-factor defficient strain). The following Streptomyces, bacteria with complex life cycle, were used in this study: S.rimosus, S.coelicolor, and S.griseus. Western blot analyses confirmed specific phosphorylation pattern in different Streptomyces species. The extent of SSB phosphorylation was too low too be detected in total cell free extracts. Therefore, SSB was His-tagged, expressed and purified from S.coelicolor. Cloning procedure, expression and results obtained after Western blot analyses will be discused. The preliminary data obtained with S.griseus wild type and A-factor defficient strain indicated possible role of A-factor regulatory cascade on tyrosine phosphorylation in this bacterium.

tyrosine kinases; SSB proteins

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