Honors Theses
Date of Award
2008
Document Type
Undergraduate Thesis
Department
Chemistry and Biochemistry
First Advisor
Ziaeddin Shariat-Madar
Relational Format
Dissertation/Thesis
Abstract
Bradykinin (BK) participates in the control of local blood flow and blood pressure by causing vascular hyperemia and vascular inflammation. The Bradykinin generating pathway of human plasma consists of prolylcarboxypeptidase (PRCP), prekallikrein (PK), and high molecular weight kininogen (HK). When the complex of HK-PK assembles on endothelial cells or an artificial negatively charged surface, PK is immediately converted to kallikrein by the enzyme PRCP. The formed kallikrein then autodigests HK to liberate BK. The BK that is formed then plays an important role in vascular permeability by stimulating constitutive Bradykinin B2 and inducible B1 receptors to release prostacyclin and nitric oxide. Thus, the activity of PRCP leads to vasodilation. In inflamed tissues, tissue injury or hypotensive bacteremia, BK has been shown to accumulate in the blood or plasma of patients. Since LPS possesses a negatively charged surface and the ability to stimulate an inflammatory response, the interaction of LPS with the proteins of the Bradykinin generating pathway assessed and characterized. These studies showed that the binding of LPS to HK was time dependent, dose dependent, saturable and reversible. The binding of LPS to HK was shown to occur via the positively charged amino acid residues of domain 5 interacting with the negatively charged moieties of LPS. The binding of LPS to HK was further shown to be maximal at pH 7.0 and in an isotonic environment. The binding of LPS to HK was blocked by HKH19, endotoxin free C1-Inhibitor, heparin, and W-acetylglucosamine glycan but not by lipid A with IC50S of 15 nM, 20 fig/ml, 10 nM and 10 mM, IV respectively. This novel study highlights the role HK plays in infection. This study proposes that HKH19, heparin and Cl-Inhibitor present therapeutic potential for the treatment of hypotensive bacteremia and sepsis.
Recommended Citation
Perkins, Ryan Cory, "Characterization of the Lipopolysaccharide Binding Site on the Plasma Protein High Molecular Weight Kininogen" (2008). Honors Theses. 2089.
https://egrove.olemiss.edu/hon_thesis/2089
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