cDNA cloning and sequence analysis of a novel calcium binding protein with oligoproline motif.

Using antibodies against pokeweed agglutinin-binding proteins from F9 embryonal carcinoma cells, we isolated a cDNA clone PW29 reacting with the antibody. mRNA hybridizing with the cDNA was 4.7 kb, and was strongly expressed in the testis, brain, kidney and heart as well as in F9 cells. The size of mRNA in the testis was heterogeneous. Sequencing the cDNA clone revealed a putative polypeptide of 70 kDa, which is rich in hydrophilic amino acids and has a characteristic sequence of (Glu(Lys))5. The protein also has an oligoproline motif, which conforms to the rule of binding capability to Src homology region III. The cDNA was translated as a fusion protein with glutathione-S-transferase, and was verified to have calcium binding activity, upon a calcium blot experiment.