Emerging structural insights into bacterial tyrosine kinases

Bacterial protein tyrosine (Tyr) phosphorylation emerged as an exciting new field of research in the last decade. Of known bacterial Tyr (BY) kinases, most regulate the production of pathogenic capsular and extracellular polysaccharide in both Gram-positive and Gram-negative bacteria. The recent publications of the first two BY kinase structures, Etk from Escherichia coli and CapB from Staphylococcus aureus, reveal that the 3D folds bear no resemblance to their mammalian counterparts but instead are similar to those of the MinD ATPases from the P-loop NTPase superfamily. These structural studies provided the first glimpse into the functional machinery of BY kinases, including their enzymatic specificity and unique activation mechanisms, which are unlike anything observed in mammalian tyrosine kinases.