A kinome of 2600 in the ciliate Paramecium tetraurelia.

Protein kinases play a crucial role in the regulation of cellular processes. Most eukaryotes reserve about 2.5% of their genes for protein kinases. We analysed the genome of the single-celled ciliate Paramecium tetraurelia and identified 2606 kinases, about 6.6% of its genes, representing the largest kinome to date. A gene tree combined with human kinases revealed a massive expansion of the calcium calmodulin regulated subfamily, underlining the importance of calcium in the physiology of P. tetraurelia. The kinases are embedded in only 40 domain architectures, contrasting 134 in human. This might indicate different mechanisms to achieve target specificity.