title: Plectin and IFAP-300K are homologous proteins binding to microtubule-associated proteins 1 and 2 and to the 240-kilodalton subunit of spectrin.
abstract: Structural and functional characteristics of plectin from intermediate filament preparations of rat glioma C6 cells were compared to those of the intermediate filament-associated protein of Mr = 300,000 (IFAP-300K) of baby hamster kidney cells (Yang, H.-S., Lieska, N., Goldman, A.E., and Goldman, R.D. (1985) J. Cell Biol. 100, 620-631). After radiolabeling and proteolytic digestion under varied conditions, both proteins yielded nearly identical peptide maps. Immunological cross-reactivity, co-migration on one- and two-dimensional high-resolution gels, chromatofocusing, and amino acid analysis demonstrated structural homology as well. In vivo labeling with 32Pi showed that plectin was the target for cAMP-independent protein kinases which phosphorylated 18-kDa domains at the end(s) of the molecule. Previously reported phosphorylation sites for cAMP-dependent and a newly identified site for Ca2+/calmodulin-dependent protein kinases were located on different domains. In solid-phase binding assays, plectin bound to vimentin, microtubule-associated proteins 1 and 2, the 240-kDa chain of brain fodrin, and alpha-spectrin from human erythrocytes. Similar characteristics were revealed for corresponding 300-kDa components of various other cell lines, supporting the concept that plectin is a general cytoskeletal cross-linking element, probably of multiple function.
mesh_terms: D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism; D002460:Cell Line; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D006224:Cricetinae; D000242:Cyclic AMP / Q000494:pharmacology; D005910:Glioma; D006801:Humans; D007381:Intermediate Filament Proteins / Q000378:metabolism*; D007668:Kidney; D008840:Microfilament Proteins / Q000378:metabolism; D008869:Microtubule-Associated Proteins / Q000378:metabolism*; D008970:Molecular Weight; D010766:Phosphorylation; D051190:Plectin; D011494:Protein Kinases / Q000378:metabolism; D011506:Proteins / Q000378:metabolism*; D051381:Rats; D013049:Spectrin / Q000378:metabolism*
chemical_list: D002352:Carrier Proteins; D000242:Cyclic AMP; D007381:Intermediate Filament Proteins; D008840:Microfilament Proteins; D008869:Microtubule-Associated Proteins; D051190:Plectin; D011494:Protein Kinases; D011506:Proteins; D013049:Spectrin; C495332:PLEC protein, human; C495334:Plec protein, rat