Calcium Binding Protein 39

Calcium Binding Protein 39 (CAB39) is a scaffolding protein, located at human chromosome 2q37.1 (1). In conjugation with psuedokinase STE20-Related Adaptor protein (STRAD), it regulates the activity of Serine/Threonine Kinase 11 (STK11/LKB1) tumor suppressors (2). LKB1 was discovered in 1988 and ever since then extensive research has been conducted in understanding how this protein might be regulated. It was reported that LKB1 mediates its cellular functions through interactions with a number of proteins including CAB39 and STRADalpha (3). CAB39 and STRADalpha are key proteins required for the growth suppressive function of LKB1 (4). Located on opposite surfaces of CAB39 are two binding sites that are required for it to form a complex with STRADalpha and LKB1. It was reported CAB39 plays a key role in increasing the catalytic activity of LKB1 towards its substrates (5).

Studies have shown that CAB39 along with ATP maintains STRADalpha in an “active” closed conformation which promotes LKB1 activation and its relocalization from the nucleus to the cytoplasm and this leads to a 10-fold increase in catalytic activity of LKB1 towards its substrates (5). CAB39 also enhances and stabilizes the formation of LKB1-STRADalpha complex by binding to a conserved Tri-Glu-Phe sequence at the C terminus of STRADalpha. This also stimulates the catalytic activity of LKB1 (6). CAB39 by itself is expressed in nucleus and cytoplasm. CAB39 is approximately a 40 kDa protein (341 amino acids). 

The CAB39 antibodies were generated against purified CAB39 protein. CAB39 are affinity purified over immobilized antigen based chromatography, and the purified immunoglobulin is stabilized in antibody stabilization buffer. FabGennix Int. Inc. will also provide limited quantities of antigenic blocking protein for CAB39 antibody. Antibodies to CAB39 (CAB39-101AP) will label ~40kDa protein in Western blot positive control samples for CAB39 and several other tissues. FabGennix Inc. will also conjugate antibodies with secondary enzymes (alk-Pase or HRP) or fluorescent probes upon request at nominal cost.

For research use only, not for diagnostic or therapeutic use.