Abstract
The thermodynamic parameters of the magnesium ion induced self-association of calf brain tubulin in pH 7.0, 0.01 M phosphate buffer containing 10(-4) M GTP, were determined from sedimentation velocity experiments. This reaction proceeds by an isodesmic mechanism terminated by the highly favored formation of a closed ring shaped polymer of degree of association 26 +/- 4. Analysis of the variation of the apparent dimerization constant in the isodesmic mechanism s,ows that this self-association is characterized by positive enthalpy, entropy, heat capacity, and molar volume changes, as well as the binding of one additional magnesium ion, which is probably not involved as a bridge between the protein molecules. The addition of the last monomeric subunit has a free energy which is about three times that of dimer formation. Under the conditions of these experiments, tubulin binds 48 +/- 5 magnesium ions with a free energy of --2.8 kcal/mol.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
