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Publication Date

Summer 2021

Degree Type

Thesis - Campus Access Only

Degree Name

Master of Science (MS)




Alberto A. Rascón

Subject Areas



The Aedes aegypti mosquito is an efficient biological vector of the dengue, yellow fever, zika, and chikungunya viruses, making it an essential task to stop the propagation of this mosquito. An effective means of reducing A. aegypti population might be to target the mosquito eggs. In collaboration with the University of Arizona, Cathepsin L3 (CatL3) was found to be involved in the melanization of A. aegypti eggs using RNAi knockdown. CatL3 is believed to be a cysteine protease and is found only in A. aegypti. When eggs are first laid in water, they are white, but over time they will melanize (darken) to protect the embryo and increase viability of the eggs. When CatL3 is not expressed in eggshells, melanization of the eggshells is reduced, causing them to dissolve in water. The goal of this project is to develop an inhibitor against CatL3 that can be released into the waters targeting A. aegypti eggs, interfering with melanization, and rendering the eggs unviable. Before developing inhibitors, CatL3 must be recombinantly expressed and biochemically studied. For the first time, recombinant CatL3 has been recombinantly expressed solubly in bacteria and purified out. The zymogen form of CatL3 has been found to be auto catalytic, and CatL3 has enough activity to cleave a synthetic cathepsin L substrate (Z Phe-Arg-pNA). CatL3 was found to have optimal activity at pH 7.2, instead of pH 5.2 like many other known cathepsins. This means that the necessary components for structural studies of CatL3 have been elucidated and that an inhibitor for its activity to possibly stop the melanization process, and thus A. aegypti propagation, is within reach.

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