IMMUNOPURIFICATION OF A SARCOMERIC JUNCTIONAL PROTEIN COMPLEX CONTAINING GAPDH

We have isolated a monoclonal antibody, P4B2, which localizes to multi ple anchorage junctions, namely, a subset of focal adhesions, the Z-di sk of muscle, and neuromuscular junctions. Immunopurification of the a ntigen to this antibody from chicken brain tissue yielded a complex of three prominent proteins with mobilities of 36, 30, and 18 kDa. Amino acid sequencing of the purified proteins identified the 36-kDa protei n as glyceraldehyde-3-phosphate dehydrogenase (GAPDH). The other two p rotein bands were heterogeneous, containing proteins found in the syna ptic vesicle fusion core complex. Immunolocalization of P4B2 antigen i n developing cultured muscle cells showed that the antigen is incorpor ated into Z-lines soon after the sarcomeric architecture was positive for cu-actinin. Together, the data indicate the P4B2 antigen is part o f a unique GAPDH-containing protein complex that may be involved in re inforcement of established cytoskeletal structures. (C) 1998 Academic Press.