title: Binding of pEL98 protein, an S100-related calcium-binding protein, to nonmuscle tropomyosin.
abstract: The cDNA coding for mouse fibroblast tropomyosin isoform 2 (TM2) was placed into a bacterial expression vector to produce a fusion protein containing glutathione-S-transferase (GST) and TM2 (GST/TM2). Glutathione-Sepharose beads bearing GST/TM2 were incubated with [35S]methionine-labeled NIH 3T3 cell extracts and the materials bound to the fusion proteins were analyzed to identify proteins that interact with TM2. A protein of 10 kD was found to bind to GST/TM2, but not to GST. The binding of the 10-kD protein to GST/TM2 was dependent on the presence of Ca2+ and inhibited by molar excess of free TM2 in a competition assay. The 10-kD protein-binding site was mapped to the region spanning residues 39-107 on TM2 by using several COOH-terminal and NH2-terminal truncation mutants of TM2. The 10-kD protein was isolated from an extract of NIH 3T3 cells transformed by v-Ha-ras by affinity chromatography on a GST/TM2 truncation mutant followed by SDS-PAGE and electroelution. Partial amino acid sequence analysis of the purified 10-kD protein, two-dimensional polyacrylamide gel analysis and a binding experiment revealed that the 10-kD protein was identical to a calcium-binding protein derived from mRNA named pEL98 or 18A2 that is homologous to S100 protein. Immunoblot analysis of the distribution of the 10-kD protein in Triton-soluble and -insoluble fractions of NIH 3T3 cells revealed that some of the 10-kD protein was associated with the Triton-insoluble cytoskeletal residue in a Ca(2+)-dependent manner. Furthermore, immunofluorescent staining of NIH 3T3 cells showed that some of the 10-kD protein colocalized with nonmuscle TMs in microfilament bundles. These results suggest that some of the pEL98 protein interacts with microfilament-associated nonmuscle TMs in NIH 3T3 cells.
authors.affiliation: Division of Chemotherapy, Chiba Cancer Center Research Institute, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Takenaga
authors.forename: Y
authors.initials: Y
authors.lastname: Nakamura
authors.forename: S
authors.initials: S
authors.lastname: Sakiyama
authors.forename: Y
authors.initials: Y
authors.lastname: Hasegawa
authors.forename: K
authors.initials: K
authors.lastname: Sato
authors.forename: H
authors.initials: H
authors.lastname: Endo
mesh_terms: D016475:3T3 Cells; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002135:Calcium-Binding Proteins / Q000096:biosynthesis / Q000302:isolation & purification / Q000378:metabolism*; D002461:Cell Line, Transformed; D002846:Chromatography, Affinity; D003001:Cloning, Molecular; D011905:Genes, ras; D005982:Glutathione Transferase / Q000096:biosynthesis / Q000302:isolation & purification / Q000378:metabolism; D008715:Methionine / Q000378:metabolism; D051379:Mice; D008969:Molecular Sequence Data; D009838:Oligodeoxyribonucleotides; D014176:Protein Biosynthesis; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis / Q000302:isolation & purification / Q000378:metabolism; D000071999:S100 Calcium-Binding Protein A4; D009418:S100 Proteins; D017386:Sequence Homology, Amino Acid; D014335:Tropomyosin / Q000096:biosynthesis / Q000302:isolation & purification / Q000378:metabolism*
chemical_list: D002135:Calcium-Binding Proteins; D009838:Oligodeoxyribonucleotides; D011993:Recombinant Fusion Proteins; D000071999:S100 Calcium-Binding Protein A4; D009418:S100 Proteins; C470944:S100a4 protein, mouse; D014335:Tropomyosin; D008715:Methionine; D005982:Glutathione Transferase