Biomaterial Database

A binding site for heparin in the apple 3 domain of factor XI. 1998

D H Ho, and K Badellino, and F A Baglia, and P N Walsh

Department of Biochemistry, Temple University School of Medicine, Philadelphia, Pennsylvania 19140, USA.

Since heparin potentiates activated factor XI (FXIa) inhibition by protease nexin-2 by providing a template to which both proteins bind (Zhang, Y., Scandura, J. M., Van Nostrand, W. E., and Walsh, P. N. (1997) J. Biol. Chem. 272, 26139-26144), we examined binding of factor XI (FXI) and FXIa to heparin. FXIa binds to heparin (Kd approximately 0.7 x 10(-9) M) >150-fold more tightly than FXI (Kd approximately 1.1 x 10(-7) M). To localize the heparin-binding site on FXI, rationally designed conformationally constrained synthetic peptides were used to compete with 125I-FXI binding to heparin. A peptide derived from the Apple 3 (A3) domain of FXI (Asn235-Arg266) inhibited FXI binding to heparin (Kd approximately 3.4 x 10(-6) M), whereas peptides from the A1 domain (Phe56-Ser86), A2 domain (Ala134-Ala176), and A4 domain (Ala317-Gly350) had no such effect. The recombinant A3 domain (rA3, Ala181-Val271) inhibited FXI binding to heparin (Ki approximately 1.4 x 10(-7) M) indicating that all the information necessary for FXI binding to heparin is contained entirely within the A3 domain. The A3 domain also contains a platelet-binding site (Asn235-Arg266), consisting of three surface-exposed loop structures, Pro229-Gln233, Thr741-Leu246, and Thr249-Phe260 (Baglia, F. A., Jameson, B. A., and Walsh, P. N. (1995) J. Biol. Chem. 270, 6734-6740). Only peptide Thr249-Phe260 (which contains a heparin binding consensus sequence, RIKKSKA) inhibits FXI binding to heparin (Ki = 2.1 x 10(-7) M), whereas peptides Pro229-Gln233 and Thr241- Leu246 had no effect. Fine mapping of the heparin-binding site using prekallikrein analogue amino acid substitutions of the synthetic peptide Thr249-Phe260 and alanine scanning of the recombinant A3 indicated that the amino acids Lys252 and Lys253 are important for heparin binding. Thus, the sequence Thr249-Phe260 which contains most of the binding energy for FXI interaction with platelets also mediates the binding of FXI to heparin.

UI	MeSH Term	Description	Entries
D007700	Kinetics	The rate dynamics in chemical or physical systems.
D008969	Molecular Sequence Data	Descriptions of specific amino acid, carbohydrate, or nucleotide sequences which have appeared in the published literature and/or are deposited in and maintained by databanks such as GENBANK, European Molecular Biology Laboratory (EMBL), National Biomedical Research Foundation (NBRF), or other sequence repositories.	Sequence Data, Molecular,Molecular Sequencing Data,Data, Molecular Sequence,Data, Molecular Sequencing,Sequencing Data, Molecular
D011956	Receptors, Cell Surface	Cell surface proteins that bind signalling molecules external to the cell with high affinity and convert this extracellular event into one or more intracellular signals that alter the behavior of the target cell (From Alberts, Molecular Biology of the Cell, 2nd ed, pp693-5). Cell surface receptors, unlike enzymes, do not chemically alter their ligands.	Cell Surface Receptor,Cell Surface Receptors,Hormone Receptors, Cell Surface,Receptors, Endogenous Substances,Cell Surface Hormone Receptors,Endogenous Substances Receptors,Receptor, Cell Surface,Surface Receptor, Cell
D002352	Carrier Proteins	Proteins that bind or transport specific substances in the blood, within the cell, or across cell membranes.	Binding Proteins,Carrier Protein,Transport Protein,Transport Proteins,Binding Protein,Protein, Carrier,Proteins, Carrier
D005172	Factor XI	Stable blood coagulation factor involved in the intrinsic pathway. The activated form XIa activates factor IX to IXa. Deficiency of factor XI is often called hemophilia C.	Coagulation Factor XI,Plasma Thromboplastin Antecedent,Blood Coagulation Factor XI,Factor 11,Factor Eleven,Antecedent, Plasma Thromboplastin,Factor XI, Coagulation,Thromboplastin Antecedent, Plasma
D006493	Heparin	A highly acidic mucopolysaccharide formed of equal parts of sulfated D-glucosamine and D-glucuronic acid with sulfaminic bridges. The molecular weight ranges from six to twenty thousand. Heparin occurs in and is obtained from liver, lung, mast cells, etc., of vertebrates. Its function is unknown, but it is used to prevent blood clotting in vivo and vitro, in the form of many different salts.	Heparinic Acid,alpha-Heparin,Heparin Sodium,Liquaemin,Sodium Heparin,Unfractionated Heparin,Heparin, Sodium,Heparin, Unfractionated,alpha Heparin
D006801	Humans	Members of the species Homo sapiens.	Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D000595	Amino Acid Sequence	The order of amino acids as they occur in a polypeptide chain. This is referred to as the primary structure of proteins. It is of fundamental importance in determining PROTEIN CONFORMATION.	Protein Structure, Primary,Amino Acid Sequences,Sequence, Amino Acid,Sequences, Amino Acid,Primary Protein Structure,Primary Protein Structures,Protein Structures, Primary,Structure, Primary Protein,Structures, Primary Protein
D000818	Animals	Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA.	Animal,Metazoa,Animalia
D001665	Binding Sites	The parts of a macromolecule that directly participate in its specific combination with another molecule.	Combining Site,Binding Site,Combining Sites,Site, Binding,Site, Combining,Sites, Binding,Sites, Combining