TY - JOUR
T1 - Biophysical characterization of anticoagulant hemextin AB complex from the venom of snake Hemachatus haemachatus
AU - Banerjee, Yajnavalka
AU - Lakshminarayanan, Rajamani
AU - Vivekanandan, Subramanian
AU - Anand, Ganesh Srinivasan
AU - Valiyaveettil, Suresh
AU - Kini, R. Manjunatha
N1 - Funding Information:
This work was supported in part by the Biomedical Research Council, Agency for Science and Technology, Singapore. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
Funding Information:
We thank Dr. Jörg Rösgen (University of Texas Medical Branch) and Dr. Nina Sidorova and Dr. Donald Rau (National Institutes of Health/National Institute of Child Health & Human Development/Laboratory of Physical and Structural Biology) for kindly providing us the osmolality conversion tables and also for helpful discussions, Dr. Prakash Kumar (Department of Biological Sciences, National University of Singapore) for his constructive comments and for making the manuscript more succinct and concise, Dr. Peter Kuhn, Dr. Jeremiah Joseph, Dr. Subramanian Yegneswaran (The Scripps Research Institute), and Dr. Thomas Record Jr. (University of Wisconsin-Madison) for the helpful discussion. We also thank Gayathri Subramanian (Department of Chemistry, National University of Singapore) for her help in the DLS studies. Y.B. thanks the National University of Singapore for his research scholarship.
PY - 2007/12/1
Y1 - 2007/12/1
N2 - Hemextin AB complex from the venom of Hemachatus haemachatus is the first known natural anticoagulant that specifically inhibits the enzymatic activity of blood coagulation factor VIIa in the absence of factor Xa. It is also the only known heterotetrameric complex of two three-finger toxins. Individually only hemextin A has mild anticoagulant activity, whereas hemextin B is inactive. However, hemextin B synergistically enhances the anticoagulant activity of hemextin A and their complex exhibits potent anticoagulant activity. In this study we characterized the nature of molecular interactions leading to the complex formation. Circular dichroism studies indicate the stabilization of b-sheet in the complex. Hemextin AB complex has an increased apparent molecular diameter in both gas and liquid phase techniques. The complex formation is enthalpically favorable and entropically unfavorable with a negative change in the heat capacity. Thus, the anticoagulant complex shows less structural flexibility than individual subunits. Both electrostatic and hydrophobic interactions are important for the complexation; the former driving the process and the latter helping in the stabilization of the tetramer. The tetramer dissociates into dimers and monomers with the increase in the ionic strength of the solution and also with increase in the glycerol concentration in the buffer. The two dimers formed under each of these conditions display distinct differences in their apparent molecular diameters and anticoagulant properties. Based on these results, we have proposed a model for this unique anticoagulant complex.
AB - Hemextin AB complex from the venom of Hemachatus haemachatus is the first known natural anticoagulant that specifically inhibits the enzymatic activity of blood coagulation factor VIIa in the absence of factor Xa. It is also the only known heterotetrameric complex of two three-finger toxins. Individually only hemextin A has mild anticoagulant activity, whereas hemextin B is inactive. However, hemextin B synergistically enhances the anticoagulant activity of hemextin A and their complex exhibits potent anticoagulant activity. In this study we characterized the nature of molecular interactions leading to the complex formation. Circular dichroism studies indicate the stabilization of b-sheet in the complex. Hemextin AB complex has an increased apparent molecular diameter in both gas and liquid phase techniques. The complex formation is enthalpically favorable and entropically unfavorable with a negative change in the heat capacity. Thus, the anticoagulant complex shows less structural flexibility than individual subunits. Both electrostatic and hydrophobic interactions are important for the complexation; the former driving the process and the latter helping in the stabilization of the tetramer. The tetramer dissociates into dimers and monomers with the increase in the ionic strength of the solution and also with increase in the glycerol concentration in the buffer. The two dimers formed under each of these conditions display distinct differences in their apparent molecular diameters and anticoagulant properties. Based on these results, we have proposed a model for this unique anticoagulant complex.
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U2 - 10.1529/biophysj.106.100164
DO - 10.1529/biophysj.106.100164
M3 - Article
C2 - 17704148
AN - SCOPUS:36849015841
SN - 0006-3495
VL - 93
SP - 3963
EP - 3976
JO - Biophysical journal
JF - Biophysical journal
IS - 11
ER -