Signal Transducing Adaptor Protein 1 (STAP1)

STAP1 functions as a docking protein acting downstream of Tec tyrosine kinase in B cell antigen receptor signaling. The protein is directly phosphorylated by Tec in vitro where it participates in a positive feedback loop, increasing Tec activity. A mouse ortholog, stem cell adaptor protein 1, shares 83% identity with its human counterpart.

The BRDG1 open reading frame encodes a protein of 295 amino acids. The overall structure of BRDG1 resembles those of docking proteins such as IRS1, IRS2, DOK1, or DOC2. BRDG1 is phosphorylated by TEC directly in vitro. Studies revealed, furthermore, that BRDG1 appears to function as a docking protein acting downstream of TEC in BCR signaling.