Binding of rat serum phosphorylcholine binding protein to platelets.
Rat serum phosphorylcholine binding protein (PCBP), a normal component of rat serum, inhibits in vitro aggregation of rat, rabbit and human platelets by interacting with platelets. In the present study, we have demonstrated the calcium-dependent, specific and saturable binding of 125I-PCBP to rat, rabbit and human platelets. Scatchard analysis of the binding data reveal a class of specific high-affinity binding sites with Kd values of 45.2 +/- 14.9, 26.1 +/- 8.3 and 32.2 +/- 9.9 nM on rat, rabbit and human platelets, respectively. These platelets also expressed a high capacity for binding to 125I-PCBP. The binding of 125I-PCBP to platelets was calcium- and time-dependent, and could be inhibited by phosphorylcholine (IC50 = 5.6 microM). Occupation of these binding sites by PCBP may be responsible for inhibition of platelet aggregation.
Randell
E
E
Department of Biochemistry, Memorial University of Newfoundland, St. John's, Canada.
Mookerjea
S
S
Nagpurkar
A
A
D000818:Animals; D001665:Binding Sites; D001792:Blood Platelets / Q000378:metabolism*; D002097:C-Reactive Protein / Q000378:metabolism* / Q000494:pharmacology; D002118:Calcium / Q000494:pharmacology; D006801:Humans; D007457:Iodine Radioisotopes; D007700:Kinetics; D008297:Male; D010767:Phosphorylcholine / Q000494:pharmacology; D010975:Platelet Aggregation Inhibitors; D011817:Rabbits; D051381:Rats; D011919:Rats, Inbred Strains
D007457:Iodine Radioisotopes; D010975:Platelet Aggregation Inhibitors; D010767:Phosphorylcholine; D002097:C-Reactive Protein; D002118:Calcium