Ca2+-dependent interaction of N-copine, a member of the two C2 domain protein family, with OS-9, the product of a gene frequently amplified in osteosarcoma

N-copine is a novel two C2 domain protein that shows Ca2+-dependent phospho lipid binding and membrane association. By using yeast two-hybrid assays, w e identified OS-9 as a protein capable of interacting with N-copine, We fur ther revealed that the second C2 domain of N-copine bound with the carboxy- terminal region of OS-9, Their interaction in vivo nas also confirmed by co -immunoprecipitation from 293E cells co-expressing transfected N-copine and OS-9, In vitro binding assays showed that this interaction was Ca2+-depend ent. By Northern blot analysis, N-copine and OS-9 were co-expressed in the same regions of human brain. These results reveal that OS-9 is a potential target of N-copine. (C) 1999 Federation of European Biochemical Societies.