Abstract

Porphyromonas gingivalis is an important etiological agent of periodontal disease - a disease that affects an estimated 49,000,000 people in the United States of America. Periodontal disease includes gingivitis – inflammation of the gums, and periodontitis – destruction of the teeth and their supporting tissues. Porphyromonas gingivalis is associated with the chronic form of periodontal disease in addition to several systemic diseases.

The vimA gene of P. gingivalis has been previously shown to play a significant role in the biogenesis of gingipains (trypsin-like cysteine proteases). The vimA has also been demonstrated to play a role in hemolysis, hemagglutination, autoaggregation, posttranslational protein modification, and LPS biogenesis. Though significant progress has been made in characterizing this gene, much remained unsolved prior to this work, especially as it relates to the molecular mechanisms and interactions of this protein in surface biogenesis, transport and membrane integrity. The focus of our work was to clarify the role of VimA on cell surface biogenesis. We were able to show via TEM and AFM that there were significant differences between the vimA-defective mutant (FLL92) and the wild-type (W83). Particularly, the topography of FLL92 showed numerous fine structures compared with W83, and had an irregular, loosely bound capsule. Fimbrial synthesis was also affected by the VimA mutation. FimA coupled immunogold particles localized with the abundant fimbrial appendages in FLL92, compared with only a few adhering in W83. Lectins were used to clarify the effect of the vimA mutation on the

glycosylation of outer-membrane proteins. Outer membrane proteins glycosylated with Galactose (β 1,3) N-Acetylgalactosamine, N-acetyl-α-D-galactosamine, Galactose (β 1,4) N-Acetylglucosamine, N-acetyl-D-galactosamine and Sialic Acid (N-Acetyl neuramic acid) were affected by the vimA mutation. Mass Spectrometric analysis of outermembrane and extracellular proteins identified several proteins in FLL92 that were aberrantly expressed, missing and of varying abundance. In-silico analysis of VimA predicted a likely role as an acyl transferase, with structural similarities to the FemABX family of proteins – these proteins are involved in peptidoglycans synthesis. The expression profile of lipid modified 3H labeled outer membrane proteins from FLL92 when compared with W83 was unchanged; however, a 27 kDa protein was observed in the extracellular fraction of FLL92 that was twice as abundant in FLL92 as in W83. Peptidoglycans isolated from FLL92 were shown to be dissimilar from those isolated from W83 via TEM and AFM, with a slower rate of hydrolysis when exposed to peptidoglycan specific hydrolytic enzymes. Taken together, we provide evidence that the VimA in an important regulator of membrane biogeneis, and is a putative lipid transferase.

LLU Discipline

Microbiology and Molecular Genetics

Department

Basic Sciences

School

School of Medicine

First Advisor

Fletcher, Hansel M.

Second Advisor

Duerksen-Hughes, Penelope

Third Advisor

Johnson, Mark

Fourth Advisor

Perry, Christopher

Fifth Advisor

Soto-Wegner, Ubaldo

Degree Name

Doctor of Philosophy (PhD)

Degree Level

Ph.D.

Year Degree Awarded

2011

Date (Title Page)

12-1-2011

Language

English

Subject - Local

VimA gene; Cell Surface Biogenesis; Membrane biogenesis; Putative Lipid Transferase; Gingivitas; Gingipain

Type

Dissertation

Page Count

154 p.

Digital Format

Application/PDF

Digital Publisher

Loma Linda University Libraries

Usage Rights

This title appears here courtesy of the author, who has granted Loma Linda University a limited, non-exclusive right to make this publication available to the public. The author retains all other copyrights.

Collection

Loma Linda University Electronic Theses & Dissertations

Collection Website

http://scholarsrepository.llu.edu/etd/

Repository

Loma Linda University. Del E. Webb Memorial Library. University Archives

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