Physical and chemical properties of purified tau factor and the role of tau in microtubule assembly.

摘要: This paper describes the physical and chemical properties of purified tau, a protein which is associated with brain microtubules induces assembly from tubulin. Purified tau composed four polypeptides migrate at positions equivalent to molecular weights between 55,000 62,000 during electrophoresis on sodium dodecyl sulfate/polyacrylamide gels. These are shown be closely related by peptide mapping amnio acid analysis. A comparison various techniques high weight microtubule-associated proteins indicates no apparent relationship. Tau found analytical ultracentrifugation sedimentation equilibrium have coefficient 2.6 S native 57,000. Tau, therefore, must highly asymmetric (an axial ratio 20:1 using prolate ellipsoid model), yet possess little α-helical structure as indicated circular dichroism. Isoelectric focusing shows neutral or slightly basic protein. also seen phosphorylated kinase copurifies microtubules. In process, apparently regulates formation longitudinal oligomers tubulin dimers, hence promotes ring under depolymerizing conditions microtubule polymerizing conditions. The known asymmetry molecule suggests that binding several molecules per molecule, thereby effectively increasing local concentration inducing filaments. role discussed in light reports polymerization induced particular non-physiological polycations. normal over wide range concentrations mild buffer define complete vitro system approach physiological.