Studies of the metal and DNA binding properties of the zinc(II)metalloregulatory protein, Synechococcus PCC 7942 SMTB /
Homeostatic control of intracellular metal ion concentration is an important process for all organisms. In the cyanobacteria Synechococcus, cellular response to toxic levels of Zn(II) and Cd(II) is performed by the metallothionein protein, SmtA. Regulation of the expression of this metallothionein...
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| Format: | Thesis Book |
| Language: | English |
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[Place of publication not identified] :
[publisher not identified] ;
2002.
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| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=726460401&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | Homeostatic control of intracellular metal ion concentration is an important process for all organisms. In the cyanobacteria Synechococcus, cellular response to toxic levels of Zn(II) and Cd(II) is performed by the metallothionein protein, SmtA. Regulation of the expression of this metallothionein is the purview of the SmtB protein, a trans-acting metalloregulatory transcriptional repressor. Previous characterization of SmtB has revealed that SmtB directly interacts with metal ions and that this protein-metal interaction is detrimental to SmtB-DNA interactions. However, the nature of SmtB-metal and SmtB-DNA interactions has not been extensively studied previously. Thus, to determine the nature of these interactions and how they correlate to one another, the metal binding properties and DNA binding properties of SmtB have been thoroughly and systematically studied. Results indicate that metal binding occurs at one of two mutually exclusive metal binding sites per monomer of SmtB with exceptionally high affinities (K[Zn] > 10¹¹ M⁻¹). Having determined the metal binding properties of SmtB in the absence of bound DNA, assessment of the interactions of SmtB and DNA in the presence and absence of Zn(II) were required to determine the effects of these two metal sites. Intriguingly, DNA binding by SmtB is quite complex with a large number of SmtB dimers interacting with the smtA operator and with significantly high affinities. Furthermore, the binding of SmtB to the smtA O/P appears to be cooperative and somewhat dependent upon the presence of the Cys61 residue. Analysis of the effects of metal binding on SmtB-DNA interactions reveals that only one of the metal binding sites observed was found to perform a regulatory role. More importantly, the correlation of metal affinity and DNA affinity of SmtB reveals the possibility of no free Zn(II) ions within a living cell under normal growth conditions. |
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| Item Description: | Vita. "Major Subject: Biochemistry". |
| Physical Description: | xi, 163 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilm Inc. |
| Bibliography: | Includes bibliographical references (leaves 154-161). |