Raman spectroscopic studies of ras-p21 proteins: Mechanism of GTP hydrolysis in proteins.
Item
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Title
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Raman spectroscopic studies of ras-p21 proteins: Mechanism of GTP hydrolysis in proteins.
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Identifier
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AAI9605684
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identifier
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9605684
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Creator
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Xiao, Donguang.
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Contributor
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Adviser: Robert H. Callender
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Date
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1995
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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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Biophysics, General
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Abstract
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We have studied the interactions of ras-p21 proteins, including wild type p21, mutant p21(G12V), mutant p21(G12D) and mutant p21(G12P), with guanine nucleotides, and the mechanism of GTP hydrolysis in proteins, by using nonresonance difference Raman spectroscopy.;A 30 cm{dollar}\sp{lcub}-1{rcub}{dollar} downshift observed in the P=O symmetric stretching motion of the terminal PO{dollar}\sb3\sp{lcub}2-{rcub}{dollar} group of GTP upon binding to proteins indicates the strong hydrogen bonding interactions between the {dollar}\gamma{dollar}-phosphate group of GTP and the proteins. The in-phase symmetric stretching band of the {dollar}\alpha{dollar}-PO{dollar}\sp{lcub}2-{rcub}{dollar} and {dollar}\beta{dollar}-PO{dollar}\sp{lcub}2-{rcub}{dollar} group of GTP had no significant changes upon binding to proteins. This result suggests that the hydrogen bonding environment around the {dollar}\alpha{dollar}-PO{dollar}\sp{lcub}2-{rcub}{dollar} and {dollar}\beta{dollar}-PO{dollar}\sp{lcub}2-{rcub}{dollar} group of GTP in proteins is similar with that in solution.;The downshift of the P=O symmetric stretching band indicates the decrease of the P=O bond order of the terminal PO{dollar}\sb3\sp{lcub}2-{rcub}{dollar} group of GTP, therefore the increase of the O{dollar}\sb\beta{dollar}-P{dollar}\sb\gamma{dollar} bond order in proteins. This result suggests that the mechanism of GTP hydrolysis is an associative reaction in p21 proteins.;We have also found strong interactions between p21 proteins and guanine nucleotides at the guanine ring moiety. Both the 2-amino and 6-carbonyl groups strongly hydrogen bonded with proteins.;A series of phosphate model compounds were studied by Raman spectroscopy. Our studies of mono-phosphate compounds show that the -O-P- bond order of these phosphate compounds is linearly related with the pK{dollar}\rm \sb{lcub}a{rcub}{dollar}, of their corresponding R-O-H compounds.;We have done normal mode analysis of phosphate model compounds with empirical method. We have obtained the correlation between Raman frequencies and force constants. We have also found that the Raman frequencies of phosphate compounds are very sensitive to the coupling between different vibrational modes.
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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.
