Function of the N-terminal arm of lambda repressor in operator binding /
The life cycle of bacteriophage [], lytic or lysogenic, is controlled by the [] cI repressor protein. The [] repressor protein acts by binding to its operator DNA as a homodimer. Each monomer is composed of two structural domains, C-terminal and N-terminal, connected through a flexible linker of 40...
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| Format: | Thesis Book |
| Language: | English |
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[Place of publication not identified] :
[publisher not identified] ;
1996.
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| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=739668571&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | The life cycle of bacteriophage [], lytic or lysogenic, is controlled by the [] cI repressor protein. The [] repressor protein acts by binding to its operator DNA as a homodimer. Each monomer is composed of two structural domains, C-terminal and N-terminal, connected through a flexible linker of 40 amino acid residues. The N-terminal DNA binding domain uses two DNA binding motifs to recognize operator DNA: a helix-turn-helix motif that lies in the major groove of each half site of the operator and a flexible N-terminal arm that wraps around the operator DNA to contact bases and phosphates on the back side of the operator. During the past several years of studies, my project has been focused on the function of the arms on operator binding stability and site specificity. Although only one of the two arms in homodimeric repressor is visualized in the cocrystal structure of the N-domain-OLl complex, both arms are shown to be required for optimal operator binding affinity and operator site discrimination. Heterodimeric repressors with two, one or no arms were constructed by fusing the DNA binding domains of CI to various leucine zippers. DNA binding activities of these heterodimers were tested in vivo and in vitro. The armed subunit of the 1-armed dimer preferentially binds to the consensus half site Of OR operators in vivo, suggesting that the deletion of one arm from the 2-armed dimer results in the absence of the arm that is invisible in the X-ray structure. The invisible arm helps repressor dimer discriminate between OR I and OR2. The presence of the invisible [] arm gives an additional favorable []1.5 kcal/mol free energy for binding to OR1 site under standard conditions. The favorable binding free energy contributed by the invisible arm mainly comes from the enthalpic component. The entropic contribution of the release of thermodynamically bound ions to bulk solution is not affected by the presence or absence of the invisible arm. These studies suggest that there is a sequence-specific physico-chemical interaction between the invisible arm and the nonconsensus half site of the operator DNA. |
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| Item Description: | Vita. "Major Subject: Biochemistry". |
| Physical Description: | xii, 151 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilms Inc. |
| Bibliography: | Includes bibliographical references: pages 123-135. |