Carabin is a 50kD protein belonging to the TBC1 domain family of proteins. Carabin differs from other members of the TBC1 domain protein family, which appear to play a role in the regulation of cell growth and differentiation. Studies demonstrate that Carabin is part of a negative regulatory loop for the intracellular TCR signalling pathway and acts as an inhibitor of the Ras signalling pathway. Carabin is also believed to mediate crosstalk between calcineurin and Ras. Carabin is most abundantly expressed in spleen and peripheral blood leucocytes.