Conformational change in thrombospondin induced by removal of bound Ca2+. A spin label approach.
The effect of removal of Ca2+ bound to thrombospondin (TSP) on the protein structure in solution has been investigated using ESR spin-label techniques. A maleimide spin label was selectively attached to the free thiol group presumably near the carboxyl-terminal domain in which Ca2+-binding sites are situated. The ESR spectra of spin-labeled TSP showed that the bound label undergoes a relatively fast rotational motion with an effective rotational correlation time in the nano-second time regimes. Removal of bound Ca2+ in TSP by dialyzing spin-labeled TSP from a Ca2+-containing buffer into an EDTA-containing buffer resulted in an increase in the mobility of the bound label by a factor of 2.3. The data suggest that EDTA chelation of bound Ca2+ in TSP induces a conformational change of TSP at least near the site of spin labeling.
Slane
J M
JM
Department of Radiology, Medical College of Wisconsin, Milwaukee 53226.
Mosher
D F
DF
Lai
C S
CS
D001792:Blood Platelets / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D004578:Electron Spin Resonance Spectroscopy; D006023:Glycoproteins / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D011485:Protein Binding; D011487:Protein Conformation; D013113:Spin Labels; D019699:Thrombospondins
D006023:Glycoproteins; D013113:Spin Labels; D019699:Thrombospondins; D002118:Calcium