Kinase Subfamily Trio

Kinase Classification: Group CAMK: Family MLCK: Subfamily Trio

Trio is present throughout eumetazoa, but does not always have a kinase domain. The complete protein is found as early as in Nematostella. Nematode copies (unc-73 in C. elegans) lack the C-terminal kinase domain, while a subset of insects (Drosophilids and mosquitoes, but not hymenopterans and beetles) have independently lost the kinase domain and the adjoining Ig and FN3 domains.

Human has two related genes, Trio and Trad (also known as Kalirin, Duo, Duet). They are long proteins, about 3000 AA, containing Sec 14, Spectrin RhoGEF, SH3, PH, Ig, FN3 and Kinase domains.

A draft alignment trio.aln shows presence and absence of the C-terminal regions across several metaoza. Note that many of these sequences are unimproved automated predictions and may not be entirely correct. The loss of C-terminal regions is confirmed by expressed sequences in Drosophila and C. elegans.

From 2002 to 2010, Trio proteins were classified as a family within the CAMK group. Now they are a subfamily within the MLCK family, and the Unc89/Speg/Obscurin genes that were once classified as Trio have been moved to a distinct subfamily, Unc89. Unc89 and Trio share the presence of RhoGEF and PH domains