R. Rojkjaer et al., CHARACTERIZATION OF THE INTERACTION BETWEEN BETA(2)-GLYCOPROTEIN-I AND CALMODULIN, AND IDENTIFICATION OF A BINDING SEQUENCE IN BETA(2)-GLYCOPROTEIN-I, Biochimica et biophysica acta. Protein structure and molecular enzymology, 1339(2), 1997, pp. 217-225
beta(2)-Glycoprotein I was shown to bind reversibly to calmodulin in a
Ca2+-dependent manner with a 1:1 stoichiometry, a K-d of 3 x 10(-9) M
and a Hill coefficient of 1.4. A sequence in beta(2)-glycoprotein I -
Gly-Tyr-Val-Ser-Arg-Gly-Gly-Met-Arg-Lys-Phe-Ile-) limited by Cys-32 an
d Cys-47 is suggested to be the calmodulin-binding region. This sequen
ce was the only one in beta(2)-glycoprotein I theoretically having the
ability to form a basic amphiphilic alpha-helix typical of a calmodul
in binding sequence. The peptide corresponding to this sequence was sy
nthesized and found to inhibit the interaction between beta(2)-glycopr
otein I and calmodulin with an IC50 value of 0.38 x [beta(2)-glycoprot
ein I] and to displace the beta(2)-glycoprotein I from the beta(2)-gly
coprotein I/calmodulin complex with an IC50 value of 0.90 x [beta(2)-g
lycoprotein I].