Gain of von Willebrand factor-binding function by mutagenesis of a species-conserved residue within the leucine-rich repeat region of platelet glycoprotein Ibalpha.
Glycoprotein (GP) Ibalpha, a member of the leucine-rich repeat (LRR) protein family, mediates platelet adhesion to immobilized von Willebrand factor (VWF). We investigated the role in VWF binding of charged residues in the LRR region of GP Ibalpha that are conserved in human, canine, and murine proteins. Substitution of His86 with either Ala or Glu resulted in a gain of VWF-binding function as judged by increased VWF binding in the presence of the modulators ristocetin and botrocetin and by enhanced adhesion of Chinese hamster ovary (CHO) cells expressing the mutant GP Ibalpha to immobilized VWF under conditions of flow. This is the first report of a gain-of-function phenotype resulting from mutations in the LRR region of GP Ibalpha. Because His86 is 2 nm away from the region of GP Ibalpha with the largest surface of contact with VWF, the data suggest that the LRRs regulate GP Ibalpha affinity for VWF allosterically.
Peng
Yuandong
Y
Thrombosis Research Section, Department of Medicine, Baylor College of Medicine N1317, One Baylor Plaza, Houston, TX 77030, USA.
Shrimpton
Corie N
CN
Dong
Jing-fei
JF
López
José A
JA
D000494:Allosteric Regulation; D019943:Amino Acid Substitution; D002448:Cell Adhesion; D017124:Conserved Sequence; D006801:Humans; D016296:Mutagenesis; D010641:Phenotype; D019038:Platelet Glycoprotein GPIb-IX Complex / Q000235:genetics* / Q000378:metabolism; D011485:Protein Binding / Q000235:genetics; D016415:Sequence Alignment; D014841:von Willebrand Factor / Q000378:metabolism*
D019038:Platelet Glycoprotein GPIb-IX Complex; D014841:von Willebrand Factor