Influence of Temperature on the Conformation of Canine Plasminogen: An Analytical Ultracentrifugation and Dynamic Light Scattering Study

Influence of Temperature on the Conformation of Canine Plasminogen: An Analytical Ultracentrifugation and Dynamic Light Scattering Study
Received May 13, 2005
Revised Manuscript Received August 5, 2005
Web Release Date: September 10, 2005
Jack A. Kornblatt* and Peter Schuck
Biochemistry
ACS Publications
Copyright ? 2005 American Chemical Society
Enzyme Research Group, Department of Biology, Concordia University, 7141 Sherbrooke Ouest, Montreal, Quebec, Canada H4B 1R6, and National Institutes of Health, Building 13, Room 3N17, 13 South Drive, Bethesda, Maryland 20892
Abstract:
Plasminogen is known to undergo an extremely large conformational change when it binds ligands; the two well-established conformations are either closed (absence of external ligand) or open (presence of external ligand). We show here that plasminogen is more complicated than can be accommodated by a two-state, closed/open, model. Temperature changes induce large structural changes which can be detected with either dynamic light scattering or analytical ultracentrifugation. The temperature-induced changes are not related to the classical closed/open conformational change since both closed and open forms of the protein are similarly influenced. It appears as though the packing density of the protein increases as the temperature is raised. Over the range 4-20 C, the Stokes' radius of the classical closed plasminogen goes from 4.7 to 4.2 nm, and that of the classical open form goes from 5.55 to 5.0 nm. These changes in packing can be rationalized if temperature change induces a large conformational change and if this is accompanied by a large change in hydration, by a change in solute binding, or by a change in the total void volume of the protein.
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