The protein kinases of Caenorhabditis elegans: a model for signal transduction in multicellular organisms

Abstract

Caenorhabditis elegans should soon be the first multicellular organism whose complete genomic sequence has been determined. This achievement provides a unique opportunity for a comprehensive assessment of the signal transduction molecules required for the existence of a multicellular animal. Although the worm C. elegans may not much resemble humans, the molecules that regulate signal transduction in these two organisms prove to be quite similar. We focus here on the content and diversity of protein kinases present in worms, together with an assessment of other classes of proteins that regulate protein phosphorylation. By systematic analysis of the 19,099 predicted C. elegans proteins, and thorough analysis of the finished and unfinished genomic sequences, we have identified 411 full length protein kinases and 21 partial kinase fragments. We also describe 82 additional proteins that are predicted to be structurally similar to conventional protein kinases even though they share minimal primary sequence identity. Finally, the richness of phosphorylation-dependent signaling pathways in worms is further supported with the identification of 185 protein phosphatases and 128 phosphoprotein-binding domains (SH2, PTB, STYX, SBF, 14-3-3, FHA, and WW) in the worm genome.

Figure 1

Hyperbolic tree representation of C. elegans protein kinases. Major protein kinase groups are labeled in different colors. A java tool for viewing this dendrogram can be found at www.kinase.com.

Figure 2

Schematic representation of the human and C. elegans receptor protein-tyrosine kinase families. Catalytic domains are shown in yellow. The names of the human RTKs are in black, and the names of the worm RTKs are in red.