Mutations in the adenomatous polyposis coli(APC) gene are responsible for familial adenomatous polyposis coli(FAP) and sporadic colorectal tumours. APC gene encodes a protein with multiple function domains and different phosphorylation states. APC is involved in regulating cell adherin,migration,prolification,through its interation with multiple proteins.APC binds to microtubles with its C terminal region directly and indirectly, but APC' middle region could also bind to microtubles,but the mechanism is still unclear.For further studying the interactions of APC and other proteins, using the middle fragment of APC(1 500 bp～4 800 bp)as bait, through yeast two-hybrid technology screen the human fetal brain cDNA library, got a novel APC binding protein SMAP/KAP3,and then generated the SMAP/KAP3 antiserum and the flowing coimmunoprecipitation and coimmunofluoresce staining identificated the interaction of APC and SMAP/KAP3.This suggested that the APC utilize the SMAP/KAP3-KIF3A-KIF3B as a motor protein move along the microtubles.