Complex formation between gamma-immunoglobulin and calmodulin in calcium-free conditions.
We show that gamma-immunoglobulin (IgG) binds calmodulin (CaM) in a Ca(2+)-independent manner, with Kd value of (1.7 +/- 0.5) x 10(-7) M. A single IgG molecule maximally bound 10 CaM molecules. The binding is to the heavy chain or Fab portion, but not the Fc portion, of the IgG molecules. Ca2+ greatly diminished the interaction between IgG and CaM, with IC50 = 8-9 microM. These data give a novel insight into protein-protein interactions.
Takeuchi
Y
Y
Banyu Tsukuba Research Institute, Ibaraki, Japan.
Birckbichler
P J
PJ
Patterson
M K
MK
D000818:Animals; D001665:Binding Sites; D015153:Blotting, Western; D002118:Calcium / Q000494:pharmacology*; D002147:Calmodulin / Q000378:metabolism*; D002645:Chickens; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D007140:Immunoglobulin Fab Fragments / Q000378:metabolism; D007074:Immunoglobulin G / Q000378:metabolism*; D007143:Immunoglobulin Heavy Chains / Q000378:metabolism; D011485:Protein Binding
D002147:Calmodulin; D007140:Immunoglobulin Fab Fragments; D007074:Immunoglobulin G; D007143:Immunoglobulin Heavy Chains; D002118:Calcium