Kinase Group TKL

The TKL group is the newest and most diverse of the standard kinase groups. Families within the group are relatively weakly related to each other, and all are also similar to members of the TK (Tyrosine Kinase) group.

Evolution

The TKL group is found in almost all eukaryotes, including Dictyostelium, plants, and vertebrates. However, it is conspicuously absent from the yeast (S. cerevisiae) kinome. There are large expansions in Dictystelium (in families that may act as tyrosine kinases, including receptor tyrosine kinases) and in plants, which the group contains the LRRK family of defense kinases (check).

Families

Within metazoans, there are seven TKL families

MLK Mixed Lineage Kinases, named after their sequence similarity to both tyrosine and serine/threonine kinases. Act frequently in MAPK cascades, as MAP4K kinases.

RAF The Raf family also acts as MAP4K, typically coupling ras-like small GTPases to growth response signals.

STKR These Serine Threonine Kinase Receptors include the TGFb and activin receptors. These are cell surface receptors which are dimers, with one member each from the two subfamilies within this family.

LRRK Leucine Rich Repeat Kinases, named after their domain structure. Little studied, outside of Dictyostelium, one has been recently implicated as a genetic cause of Parkinson's Disease.

LISK Consists of two subfamilies which are closely related in sequence, though not by any known common function. These are the LIMK (LIM domain Kinase) and TESK (Testis Expressed Serine Kinase) subfamilies.

IRAK IL1-R associated Kinase

RIPK Receptor Interacting Protein Kinase.

A further 7 families have been defined within the Dictyostelium kinome, and no complete analysis has yet been carried out on plant TKLs.