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33 卷 2 期 结 构 化 学 (JIEGOU HUAXUE) Vol. 33, No. 2
2014. 2 Chinese J. Struct. Chem. 216─222
Maltose-binding Protein Improving
the Crystallizability of C2 Domain
of Human Coagulation Factor V
①
CHEN Song
a, b
WANG Yu
a, b
ZHAO Bao-Yu
a, b
CHEN Zhuo
a
HUANG Ming-Dong
a②
a
(State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the
Structure of Matter, Chinese Academy of Sciences, Fuzhou 350002, China)
b
(Graduate School of Chinese Academy of Sciences, Beijing 100039, China)
ABSTRACT Human coagulation Factor V (FV), together with Factor Xa, assembles to prothrombi-
nase complex on activated cell surface, which converts prothrombin into thrombin, leading to fibrin
deposition. The C2 domain of FV is believed to be a primary anchor for the assembly of pro-
thrombinase on the cell surface, and was proposed as a target to intervene with pathological thrombotic
events. We report here the crystal structure of the C2 domain of FV fused to maltose-binding protein
(MBP). The fusion tag of MBP is critical to generate the crystal for this study. There is no strong
interaction between MBP and FVC2. The overall structure of FVC2 is similar to the previous FVC2
structures, suggesting the MBP fusion does not perturb the molecular structure of FVC2. This crystal
form of FVC2 can be used for future study of molecular interaction between FVC2 and its inhibitors.
Keywords: maltose-binding protein, coagulation factor V, protein crystallizability
1 INTRODUCTION
Blood coagulation is an important host defense me-
chanism, which involves a series (or "cascade") of
precursor protein (zymogen) activation. At each stage
a zymogen is converted to an active protease by
cleavage of one or two peptide bonds of the zymogen.
Thrombin is the last protease in the cascade, con-
verting fibrinogen to fibrin. Thrombin is generated
from prothrombin by factor Xa. The presence of
activated factor V (FVa) greatly enhances the pro-
teolytic efficiency of factor Xa
[1-2]
, making FVa an
essential cofactor in hemostasis. Besides FVa,
activated factor VIII (FVIIIa) is another key cofactor
in the blood coagulation cascade, which enhances the
proteolytic activity of factor IXa. Both activated
cofactors VIIIa and Va are highly specific for their
cognate proteinases and have the same A1-A2-B-A3-
C1-C2 domain architecture
[3]
. The C2 domains of both
FV and FVIII were believed to be the key domain
anchoring FVa and FVIIIa onto the cell membrane
where blood coagulation happens. Structural studies
showed that FV C2 domain (abbreviated as FVC2)
comprises a distorted jelly-roll β-barrel motif and two
surface exposed loops (named spikes) containing
hydrophobic/aromatic residues that are responsible for
the anchoring of C2 domain to the cell surface. We
also identified an exposed region of C2 domain
(Trp
2313
-His
2315
) as another cell surface anchor point
[4]
.
Intervention of C2 domain docking to cell membrane
has been proposed as a unique strategy to develop
anticoagulants to treat a number of thrombotic events.
Received 4 June 2013; accepted 27 November 2013
① Supported by the National Natural Science Foundation of China (31161130356)
② Corresponding author. E-mail: mhuang@fjirsm.ac.cn