Characterization of Bruton's Tyrosine Kinase Gene and Protein from Marine Sponge Suberites domuncula

Bruton's tyrosine kinase (Btk) is a member of Tec family of protein tyrosine kinases. It is expressed in B cells and myeloid cells in humans and it is crucial for maturation of B-lineage lymphoid cells. Mutations in the gene encoding human Btk result in hereditary immunodeficiency X-linked agammaglobulinemia. Sponge proteins can probably reflect characteristics of the ancestral metazoan homologues before their diversifications and specializations in complex animals. Gene coding for sponge Btk-like protein was fully characterized and its structure was compared with homologous genes from other organisms. Kinase activity of sponge protein was compared to human Btk activity. We showed that sponge Btk-like gene is probably the most ancient member of Tec family while other members arose from the ancestral gene present in chordate ancestor. The ancestral-type protein was structurally and functionally similar to the highly sophisticated enzyme it is today, whose functions are usually associated with higher Metazoa. (doi: 10.5562/cca1862)