Document Type

Open Access Thesis

Embargo Period

9-2-2015

Degree Program

Biochemistry

Degree Type

Master of Science (M.S.)

Year Degree Awarded

2015

Month Degree Awarded

September

Abstract

Chaperone proteins are essential components in the maintenance and turnover of the proteome. Many chaperones play integral functions in the folding and unfolding of cellular substrates under many conditions, including heat stress. Most chaperones can be characterized into two categories; the typical ATP dependent chaperones and the ATP independent chaperones. One ATP independent chaperone class it the Small Heat Shock Proteins (sHSPs), which as molecular life vests and are thought to protect misfolding proteins from irreversible aggregation. One such organism, the cyanobacterium Synechocystis sp. PCC 6803, is an excellent model for the study and understanding of these proteins and their functions in vivo. The genome of Synechocystis encodes only one sHSP, Hsp16.6, and it has be shown to be essential for acquired thermotolerance. Two mutant derivatives of Hsp16.6 with single amino acid substitutions in the N-terminal arm (L9P and E25K) have loss-of-function phenotypes similar to knock out strains, but each has very different biochemical properties. The mutant L9P has an inability to interact with putative substrates during heat stress in vivo, while the mutant E25K appears unable to release substrates. Using a directed evolution approach, suppressors have been isolated that recover the lost thermotolerance of their respective parent strains, either L9P (16 suppressors) or E25K (10 suppressors). Illumina sequencing and comparative genomics have been used to identify alterations in the genomes of the suppressor strains in order to define genetic circuits involved in thermotolerance.

First Advisor

Elizabeth Vierling

Second Advisor

Danny Schnell

Third Advisor

Courtney Babbit

Fourth Advisor

Steven Sandler

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