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Binding of platelet glycoprotein Ibβ through the convex surface of leucine‐rich repeats domain of glycoprotein IX
Author(s) -
MO X.,
NGUYEN N. X.,
MCEWAN P. A.,
ZHENG X.,
LÓPEZ J. A.,
EMSLEY J.,
LI R.
Publication year - 2009
Publication title -
journal of thrombosis and haemostasis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.947
H-Index - 178
eISSN - 1538-7836
pISSN - 1538-7933
DOI - 10.1111/j.1538-7836.2009.03536.x
Subject(s) - ectodomain , glycoprotein , leucine rich repeat , platelet glycoprotein gpib ix complex , chimera (genetics) , chinese hamster ovary cell , platelet membrane glycoprotein , protein subunit , biology , microbiology and biotechnology , genetics , chemistry , gene , receptor
Summary.  Background : The mechanism of assembly of the platelet glycoprotein (GP) Ib‐IX complex from GPIbα, GPIbβ and GPIX subunits is not entirely clear. In this complex, ectodomains of both GPIbβ and GPIX subunits contain two leucine‐rich repeats (LRR) and share high sequence similarity. However, they differ noticeably in stability, hampering further analysis of their interaction. Objectives and methods : Guided by analysis of the LRR structure, we report a well‐folded Ibβ/IX chimera and its usage in dissecting GPIX function. Results : In this chimera, three non‐contiguous sequences that may constitute the putative convex surface of the GPIbβ ectodomain are replaced by their GPIX counterparts. Like GPIbβ but unlike GPIX ectodomain, it can secrete from transfected Chinese hamster ovary cells and fold into a stable conformation. Furthermore, replacing the ectodomain in GPIX with the Ibβ/IX chimera, but not the GPIbβ ectodomain, preserved its interaction with GPIbβ as demonstrated by its native‐like GPIbβ‐induced increase in surface expression and coimmunoprecipitation. Conclusions : The putative convex surface of the LRR domain in GPIX is sufficient, in the context of full‐length subunit, to mediate its association with GPIbβ.

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