Purification, immunological and biochemical characterization of an Ap4A binding protein from Xenopus laevis oocytes

Diadenosine 5′,5″′-P1, P4-tetraphosphate (Ap4A) binding protein specifically binds Ap4A. The protein has been purified from Xenopus laevis oocytes and presents and estimated molecular weight of 100,000 by gek filtration. In the first stages of the purification, the Ap4A binding activity is found associated to DNA polymerase alpha-DNA primase, forming heterogeneous high molecular weight complexes.A monoclonal antibody has been prepared against the purified Ap4A binding protein. The antibody partially neutralizes the Ap4A binding activity. Using the immunoblot technique, it has been shown that the antibody is able to recognize either native or SDS-denaturated Ap4A binding protein. The monoclonal antibody immoreacted with a polypeptide of 90,000 which coincides with the molecular weight obtained by get chromatography and indicates that the native Ap4A binding protein from Xenopus oocytes is probably a monomeric protein. © 1988 IRL Press Limited.