Faculty Collaboration Database

The cysteine knot of platelet glycoprotein Ib beta (GPIb beta) is critical for the interaction of GPIb beta with GPIX. Blood 2002 Jun 15;99(12):4428-33

Date

05/31/2002

Pubmed ID

12036872

DOI

10.1182/blood.v99.12.4428

Scopus ID

2-s2.0-0037097592 (requires institutional sign-in at Scopus site)   17 Citations

Abstract

The glycoprotein Ib (GPIb) complex is composed of GPIb alpha covalently attached to GPIb beta and noncovalently complexed with GPIX and GPV. Patients with Bernard-Soulier syndrome demonstrate that mutations in either GPIb beta or GPIX result in an absence of platelet GPIb alpha. This occurs through the interaction of GPIX with GPIb beta. The precise sites of interaction of GPIb beta with GPIX are not known. To characterize the interaction of GPIb beta and GPIX, we developed an anti-GPIb beta monoclonal antibody MBC 257.4, whose epitope was in the N-terminal region of GPIb beta. N-terminal truncations of GPIb beta were expressed in mammalian cells. N-terminal truncations of GPIb beta, missing the first 14, 26, or 31 amino acids, were surface-expressed but did not enable coexpressed GPIX to be surface expressed, suggesting that the site of interaction with GPIX was modified by these deletions. GPIb beta and GPIX chimeras corresponding to predicted boundaries were used to define the sites of interaction of GPIb beta with GPIX. Replacing the N-terminal disulfide loops of GPIb beta (amino acids 1-14) with the corresponding disulfide loops of GPIX (amino acids 1-22) resulted in surface expression of coexpressed wildtype GPIX. However, when the N terminus of GPIb beta was replaced to residue 32 with the N terminus of GPIX (amino acids 1-36), GPIX did not surface express with this chimera. These results suggest that the cysteine knot region of GPIb beta in the N terminus is critical for the conformation of GPIb beta that interacts with GPIX and further suggests that a critical interaction of GPIb beta with GPIX involve residues 15 through 32 of GPIb beta

Author List

Kenny D, Morateck PA, Montgomery RR

Author

Robert R. Montgomery MD Adjunct Professor in the Pediatrics department at Medical College of Wisconsin

MESH terms used to index this publication - Major topics in bold

Antibodies, Monoclonal
Bernard-Soulier Syndrome
Binding Sites
Cell Line, Transformed
Cysteine
Epitope Mapping
Frameshift Mutation
Humans
Mutagenesis, Site-Directed
Platelet Glycoprotein GPIb-IX Complex
Protein Binding
Protein Structure, Tertiary
Transfection