Structure and function of the first epidermal growth factor-like module in human factor IX.
Item
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Title
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Structure and function of the first epidermal growth factor-like module in human factor IX.
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Identifier
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AAI9315468
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identifier
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9315468
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Creator
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Huang, Linda Hao Tsai.
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Contributor
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Adviser: William V. Sweeney
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Date
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1993
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Language
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English
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Publisher
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City University of New York.
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Subject
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Chemistry, Biochemistry
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Abstract
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Epidermal growth factor (EGF) is a small mitogen which consists of 53 amino acids. During the last decade, a large number of EGF-like molecules have been found. There are at least two groups of EGF-like modules. Both classes of modules have three pairs of disulfide bonds in homologous arrangement in a pattern of cysteine residues 1-3, 2-4, and 5-6. The major difference between these two groups of modules is that the modules in the first group have high affinity for the EGF-receptor, and can lead to mitogenic responses in EGF-sensitive cells; the second group of modules are found in a wide range of proteins with diverse biological function. Among these proteins are vitamin K-dependent clotting factors VII, IX, and X, protein C and protein S, and the non-vitamin K-dependent proteins urokinase (uPA), tissue-type plasminogen activator (tPA), and factor XII. The functions of these modules are not fully understood.;To investigate the biological role of the EGF-like modules in the second group mentioned above, the first EGF-like module (45-87) of human factor IX (FIX-EGF1) has been chemically synthesized by the solid phase method. The synthesized peptide has been refolded, and characterized.;Efforts have been made to mimic putative EGF-like activities by synthesizing different chimeric EGF analogs with the first EGF-like module in factor IX (FIX-EGF1) as a non-active frame. However, no analog with significant EGF-like activity has been obtained.;Calcium plays an important role as a cofactor in the blood clotting system. The calcium binding site in the EGF-like region in factor IX has been reported to be of functional importance. The calcium binding with the synthesized FIX-EGF1 has been examined, leading to the identification of a calcium binding site in this module. The function of the metal ion binding is more likely to orient, and to stabilize the factor IX molecule as a whole rather than to change the structure of the module itself.;The two dimensional {dollar}\sp1{dollar}H nuclear magnetic resonance spectra (2D {dollar}\sp1{dollar}H NMR) of FIX-EGF1 have been acquired. The sequence specific resonance assignment and the secondary structure of the module have been determined. It has been found that the peptide has two antiparallel {dollar}\beta{dollar}-sheets. The first sheet consists of residues 16-20 and 25-29, the second sheet consists of 32-34 and 40-42. A {dollar}\beta{dollar}-turn has been observed at one end of the each sheet. The tertiary structure has been determined by distance geometry calculation with the NOE constraints using DSPACE, followed by energy minimization refinement with the program AMBER. The solution structure indicates that there are two subdomains in the peptide consisting of 1-28 and 29-43. The structure is substantially similar to that of EGF, but differences in the degree of the NH{dollar}\sb2{dollar}-terminal {dollar}\beta{dollar}-sheet twist, and the C-terminal tail orientation are observed.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
