Kinase Subfamily FAM20B
Kinase Classification: Group Atypical: Family FJ: Subfamily FAM20B
FAM20B is a subfamily of the Four-Jointed family of secretory kinases. It consists of a single gene in humans, all other vertebrates, some other chordates and echinoderms, insects and cnidarians. It is not found in nematodes or outside of the eumetazoans.
Protein Structure
Like other FJ family kinases, FAM20B has a conserved signal peptide but no predicted transmembrane domain. The PKL-type kinase domain is at the C-terminus, with a variable (~200? AA) N-terminus with no known domain and lower sequence conservation than the kinase domain.
Protein Interactions
Neither human nor Drosophila FAM20B proteins have reported protein interactions (Mar 2010)
Phylogeny Notes
[more detail]
Functions
FAM20B was shown to have in vitro kinase activity on glycosylated proteins, specifically phosphorylating xylose residues [1]. Thus it has a protein substrate, but phosphorylates a sugar moiety rather than an amino acid. The level of chondroitin and heparan sulfate in HeLa cells was shown to correlate positively with the level of FAM20B expression.
The zebrafish FAM20B has also been implicated in proteoglycan production: A conference abstract found two of three mutations in a screen for cartilage formation in zebrafish to be in FAM20B. These mutations, and morpholinos against FAM20B caused increased production of cartilage matrix and decreased perichondral bone formation during endochondral ossification (bone formation) (Eames et al, Dev Biol 319:480). The other mutation was found in a proteoglycan enzyme, and it was shown that the two proteins operate together in the formation of proteoglycans
