Identifier

etd-04032013-120222

Degree

Doctor of Philosophy (PhD)

Department

Biological Sciences

Document Type

Dissertation

Abstract

The DedA protein family is a highly conserved family of membrane proteins, with members present throughout all domains of life: Bacteria, Archaea, and Eukarya. Investigation of the DedA membrane protein family began with the isolation of BC202, an Escherichia coli mutant with in-frame deletions of two DedA proteins of unknown function (YqjA and YghB) that share 61% amino acid identity. BC202 demonstrates temperature sensitivity, inefficient cell division, an altered phospholipid composition, increased expression of extracytoplasmic stress response pathways, as well as an inability to maintain the cell membrane proton motive force (PMF). Additionally, Borrelia burgdorferi has a single DedA homolog (Bb0250), deletion of this gene was only possible in the presence of a cloned and inducible copy of the gene. The essentiality of the DedA membrane protein family in B. burgdorferi, instigated the investigation into the essentiality of the family in E. coli, which has eight individually non-essential DedA genes. Discussed herein is the generation of mutants in which all eight E. coli DedA genes are deleted, which again, was only possible in the presence of a cloned and arabinose inducible DedA protein. One mutant was further characterized, BAL801 (cloned EcDedA), identifying that the essential function of the E. coli DedA membrane protein family may be to play a vital role in the proper maintenance and segregation of the bacterial nucleoid. Also, complementation of BC202’s temperature sensitivity and cell division defects are complemented by only four of the eight E. coli DedA proteins (C-group; yqjA, yghB, yohD, and yabI), the remaining four were subsequently classified as non-complementing (NC-group; ydjX, ydjZ, yqaA, and dedA). The identification of the C- and NC-groups within E. coli’s DedA proteins, lead to the generation of another mutant series in which the NC-group and the C-group proteins were independently deleted, to aide in the continued understanding of this essential and redundant membrane protein family.

Date

2013

Document Availability at the Time of Submission

Release the entire work immediately for access worldwide.

Committee Chair

Doerrler, William T.

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