Honors Theses
Date of Award
2009
Document Type
Undergraduate Thesis
Department
Chemistry and Biochemistry
First Advisor
Randy Wadkins
Relational Format
Dissertation/Thesis
Abstract
While the presence of water within biological systems is acknowledged to be of utmost importance, its specific role at the molecular level within these systems has only recently been studied carefully. Of particular interest are the effects of water on the interactions that occur between topoisomerase-I and DNA. Topoisomerase-I relaxes supercoiled DNA, a process critical for cellular processes such as transcription and replication. Relaxation occurs when the enzyme breaks one strand of the double-stranded DNA, rotates a broken end around the intact strand, and rejoins the two broken ends. consequently changing the linking number of the supercoiled DNA by an increment of one. While it is well known that water acts during the catalytic mechanism of the enzyme to hydrolyze the phosphate backbone, other effects of water have not been explored. Through the osmotic stress method, the role and amount of water involved in the interaction between topoisomearase-I and DNA with regard to enzymatic activity has been investigated. Four osmolytes (PEG 6000, PEG 600, betaine, and sucrose) were introduced into the reaction at varying concentrations (molality), which is related to the osmotic pressure (osmolality). Results of the osmolytes on the catalytic activity of the enzyme were visualized and analyzed through the quantification of topoisomer band 111 intensity, providing the percentage of DNA under these conditions that is converted to the relaxed form. Our preliminary data suggests that the presence of osmolytes attenuates the catalytic activity of topoisomerase-I. Thus, it appears that water may play an important role in stabilizing the enzyme-substrate complex, enabling normal catalytic activity of topoisomerase-I. IV
Recommended Citation
Dukes, Matthew Paul, "The Osmolytic Effect and Its Action on Topoisomerase-I" (2009). Honors Theses. 1991.
https://egrove.olemiss.edu/hon_thesis/1991
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