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Zinc Homeostasis in E. coli

Hensley, Mart Patrick
http://rave.ohiolink.edu/etdc/view?acc_num=miami1333655875

Abstract Details

2012, Doctor of Philosophy, Miami University, Chemistry and Biochemistry.
The homeostasis of transition metal ions is critical to the survival of all organisms. Zinc (Zn(II)) is one of the most important transition metals found in biological systems; however, the homeostasis of this metal is poorly understood. Previous studies have shown that intracellular Zn(II) levels in E. coli are in the low millimolar range, yet there is less than one “free” (unbound) Zn(II) ion per cell. There must exist in the E. coli cell a mechanism for the delivery and insertion of Zn(II) into proteins. The cytoplasmic transport of other transitions metals, such as copper, iron, nickel, manganese, and arsenic, is accomplished by a group of proteins called metallochaperones. No such metallochaperone has been identified for Zn(II). Since none of the available models for intracellular Zn(II) transport are able to explain adequately Zn(II) homeostasis in E. coli, we hypothesized a new model. This model proposes that Zn(II) is delivered to Zn(II) metalloproteins as the proteins are translated and exiting the ribosome. In the co-translational model for Zn(II) homeostasis, the first datum that must be accounted for is the constant presence of 0.2 mM Zn(II) in E. coli. In Chapter 2 it is shown that the ribosome binds significant amounts of Zn(II). This ribosomal storage accounts for millimolar amounts of intracellular Zn(II). In Chapters 3 and 4 studies on several ribosomal proteins (L31, L13, L22, L24, and L29) are presented in an effort to identify Zn(II) binding proteins that could transfer Zn(II) to nascent proteins. Our data show that soluble L31 adopts a unique Zn(II) binding motif containing one cysteine and histidine. This Zn(II) binding site is reminiscent of the Cu(I) binding site of ATX1, a copper metallochaperone. Close examination of the E. coli ribosome crystal structures shows that L31 does not bind Zn(II) with the same binding site as in solution. By accounting for all known data about Zn(II) homeostasis in E. coli, it is hypothesized that ribosomal protein L31, while in solution and not bound to the ribosome, acts as a Zn(II) metallochaperone, delivering Zn(II) to nascent proteins as they exit the ribosome.
Michael Crowder, Dr. (Advisor)
Carole Dabney-Smith, Dr. (Committee Member)
Christopher Makaroff, Dr. (Committee Chair)
David Tierney, Dr. (Committee Member)
Gary Janssen, Dr. (Committee Member)
80 p.
Biochemistry
Zinc homeostasis; metal ion transport

Recommended Citations

Citations

  • Hensley, M. P. (2012). Zinc Homeostasis in E. coli [Doctoral dissertation, Miami University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=miami1333655875

    APA Style (7th edition)

  • Hensley, Mart. Zinc Homeostasis in E. coli. 2012. Miami University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=miami1333655875.

    MLA Style (8th edition)

  • Hensley, Mart. "Zinc Homeostasis in E. coli." Doctoral dissertation, Miami University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=miami1333655875

    Chicago Manual of Style (17th edition)

miami1333655875
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© 2012, all rights reserved.
This open access ETD is published by Miami University and OhioLINK.