Binding of microtubule-associated protein 2 and tau to the intermediate filament reassembled from neurofilament 70-kDa subunit protein. Its regulation by calmodulin.
Two major brain microtubule-associated proteins (MAPs), MAP2 and tau, were found to bind to the intermediate filaments reassembled from neurofilament 70-kDa subunit protein (= 70-kDa filaments). The binding was saturable. The apparent dissociation constant (KD) for the binding of MAP2 to the 70-kDa filaments was estimated to be 4.8 X 10(-7) M, and the maximum binding reached 1 mol of MAP2/approximately 30 mol of 70-kDa protein. The apparent KD for the tau binding was 1.6 X 10(-6) M, and the maximum binding was 1 mol of tau/approximately 3 mol of 70-kDa protein. It was also found that MAP2 and tau did not compete with each other for binding to the 70-kDa filaments. Most interestingly, calmodulin, a ubiquitous Ca2+-binding protein in eukaryotic cells, was found to inhibit the binding of MAP2 and tau to the 70-kDa filaments. The inhibition by calmodulin was regulated by changes in Ca2+ concentration around 10(-6) M, and was canceled by trifluoperazine, a calmodulin inhibitor.
D000818:Animals; D001923:Brain Chemistry; D002118:Calcium / Q000378:metabolism; D002147:Calmodulin / Q000494:pharmacology*; D003599:Cytoskeleton / Q000378:metabolism*; D007381:Intermediate Filament Proteins / Q000378:metabolism*; D007382:Intermediate Filaments / Q000378:metabolism*; D007700:Kinetics; D046911:Macromolecular Substances; D008869:Microtubule-Associated Proteins / Q000378:metabolism*; D008970:Molecular Weight; D016900:Neurofilament Proteins; D013552:Swine; D013696:Temperature; D014268:Trifluoperazine / Q000494:pharmacology; D016875:tau Proteins
D002147:Calmodulin; D007381:Intermediate Filament Proteins; D046911:Macromolecular Substances; D008869:Microtubule-Associated Proteins; D016900:Neurofilament Proteins; D016875:tau Proteins; D014268:Trifluoperazine; D002118:Calcium