Component of a complex that binds and activates STK11/LKB1. In the complex, required to stabilize the interaction between CAB39/MO25 (CAB39/MO25alpha or CAB39L/MO25beta) and STK11/LKB1. . This is the function of Ensembl gene identifier ENSG00000135932 (CAB39, calcium binding protein 39).