Tyrosine kinases in bacteria

[Jim Woodgett]

In article <38dtd5$2sk at network.ucsd.edu>, T. S. Pillay <tpillay at ucsd.edu> 
writes:
 
> It is believed that bacteria do not have tyrosine kinases yet 
> some bacteria have tyrosine phosphatases eg the yersinia 
> enterocolitica PTPase-  why is this so?  Are there bacterial 
> tyrosine kinases which have not been discovered? 
  
Good question. There are some interesting reviews from several labs working on 
the Yersinia phosphatases (which also dephosphorylate Ser/Thr) which address 
this point.  The YOP phosphatase is a virulence factor and thus likely 
contributes to the pathogenicity of the baccillae perhaps by screwing up the 
tyrosine phosphorylation pathways of the (mammalian) host.  Look up Jack 
Dixon's reviews if you need more.

Yeast also do not appear to have receptor or Src-like tyrosine kinases.  There 
is Tyr phosphorylation in yeast (cdc2, Mck1, etc.) but the kinases responsible 
look like Ser/Thr kinases and expression of Src in yeast is deleterious to 
growth (unless Csk1 is co-expressed).

According to Tony Hunter who has extrapolated from the geneome sequencing 
project data, there are around 2000 kinases in the human genome and maybe 1000 
phosphatases.  The current number of identified kinases is about 200 so 
there's plenty of scope for new discovery.  However, there is little chance of 
a "classic tyrosine kinase" in bacteria as these organisms have evolved very 
different protein kinase structures from eukaryotes (inc. Ser/Thr kinases).  
Of course, next week one will be published...  ;-)

Jim