title: Photocrosslinking of calmodulin and/or actin to chicken gizzard caldesmon.
abstract: The two sulfhydryl groups of chicken gizzard caldesmon were specifically labeled with a photoreactive crosslinker, benzophenone-maleimide, to study its interactions with calmodulin and/or actin. When incubated with F-actin caldesmon crosslinks to a single actin monomer; it can, however, crosslink to up to two calmodulin molecules in the presence, but not in the absence, of Ca2+. Thus caldesmon may have two calmodulin-binding sites, each containing, or being near, one of the two thiol residues. One of these two sites may also be adjacent to the actin-binding site. A calmodulin-binding fragment of caldesmon resulting from cyanogen bromide digestion crosslinks to a single calmodulin molecule, also in a Ca2+-dependent manner. Crosslinking of calmodulin to caldesmon does not prevent the latter from binding F-actin, suggesting that calmodulin and actin do not compete with each other for the same binding site(s) on the caldesmon molecule.
authors.affiliation: Dept. of Muscle Research, Boston Biomedical Research Institute, MA 02114.
authors.forename: C L
authors.initials: CL
authors.lastname: Wang
mesh_terms: D000199:Actins / Q000378:metabolism*; D000818:Animals; D001577:Benzophenones; D001665:Binding Sites; D002118:Calcium / Q000494:pharmacology; D002147:Calmodulin / Q000378:metabolism*; D002148:Calmodulin-Binding Proteins / Q000378:metabolism*; D002645:Chickens; D003432:Cross-Linking Reagents; D004591:Electrophoresis, Polyacrylamide Gel; D005895:Gizzard, Avian / Q000032:analysis; D046911:Macromolecular Substances; D008301:Maleimides; D010777:Photochemistry
chemical_list: D000199:Actins; D001577:Benzophenones; D002147:Calmodulin; D002148:Calmodulin-Binding Proteins; D003432:Cross-Linking Reagents; D046911:Macromolecular Substances; D008301:Maleimides; C043592:maleimide; C047723:benzophenone; D002118:Calcium