title: RNA aptamer to thrombin binds anion-binding exosite-2 and alters protease inhibition by heparin-binding serpins.
abstract: We studied the RNA aptamer Toggle-25/thrombin interaction during inhibition by antithrombin (AT), heparin cofactor II (HCII) and protein C inhibitor (PCI). Thrombin inhibition was reduced 3-fold by Toggle-25 for AT and HCII, but it was slightly enhanced for PCI. In the presence of glycosaminoglycans, AT and PCI had significantly reduced thrombin inhibition with Toggle-25, but it was only reduced 3-fold for HCII. This suggested that the primary effect of aptamer binding was through the heparin-binding site of thrombin, anion-binding exosite-2 (exosite-2). We localized the Toggle-25 binding site to Arg 98, Glu 169, Lys 174, Asp 175, Arg 245, and Lys 248 of exosite-2. We conclude that a RNA aptamer to thrombin exosite-2 might provide an effective clinical reagent to control heparin's anticoagulant action.
authors.affiliation: Department of Pathology and Laboratory Medicine, Carolina Cardiovascular Biology Center, The University of North Carolina at Chapel Hill, School of Medicine, Chapel Hill, NC 27599-7035, USA.
authors.forename: Martha L
authors.initials: ML
authors.lastname: Jeter
authors.forename: Linda V
authors.initials: LV
authors.lastname: Ly
authors.forename: Yolanda M
authors.initials: YM
authors.lastname: Fortenberry
authors.forename: Herbert C
authors.initials: HC
authors.lastname: Whinna
authors.forename: Rebekah R
authors.initials: RR
authors.lastname: White
authors.forename: Christopher P
authors.initials: CP
authors.lastname: Rusconi
authors.forename: Bruce A
authors.initials: BA
authors.lastname: Sullenger
authors.forename: Frank C
authors.initials: FC
authors.lastname: Church
mesh_terms: D000838:Anions; D000991:Antithrombins / Q000378:metabolism*; D001483:Base Sequence; D001665:Binding Sites; D006025:Glycosaminoglycans / Q000378:metabolism; D006493:Heparin / Q000378:metabolism*; D015844:Heparin Cofactor II / Q000378:metabolism*; D006801:Humans; D008958:Models, Molecular; D018046:Protein C Inhibitor / Q000378:metabolism*; D012313:RNA / Q000737:chemistry / Q000378:metabolism*; D013917:Thrombin / Q000378:metabolism*
chemical_list: D000838:Anions; D000991:Antithrombins; D006025:Glycosaminoglycans; D018046:Protein C Inhibitor; D012313:RNA; D015844:Heparin Cofactor II; D006493:Heparin; D013917:Thrombin