Graduation Year

2019

Document Type

Thesis

Degree

M.S.

Degree Name

Master of Science (M.S.)

Degree Granting Department

Biology (Cell Biology, Microbiology, Molecular Biology)

Major Professor

Gary Wayne Daughdrill, Ph.D.

Committee Member

Kristina Schmidt, Ph.D.

Committee Member

Younghoon Kee, Ph.D.

Keywords

COR15A, Intrinsically disordered proteins (IDPs), LEA, NMR

Abstract

COR15A is a cold regulated disordered protein from Arabidopsis thaliana that contributes to freezing tolerance in plants by protecting membranes. It belongs to the (LEA) Late Embryogenesis Abundant group of proteins that accumulate during the later stage of seed development and are expressed in various parts of the plant. During freezing-induced cellular dehydration, COR15A transitions from a disordered structure to a mostly α-helical structure that binds and stabilizes chloroplast membranes when cells dehydrate due to freezing. We hypothesize that increasing the transient α-helicity of COR15A under normal conditions will increase its ability to bind and protect chloroplast membranes when cells are frozen. To test this hypothesis, conserved glycine residues were mutated to alanine to increase α-helicity. NMR spectroscopy was used to examine structural changes of these mutants compared to wildtype in 0% and 20% TFE. The impact of these mutations on the stability of model membranes during a freeze-thaw cycle was investigated by fluorescence spectroscopy. The results of these experiments showed the mutants had a higher content of α-helical secondary structure than wildtype in 0% and 20% TFE. Increased α-helicity of the COR15A mutants improved membrane stabilization during freezing. Altogether, our results suggest the conserved glycine residues are important for maintaining the disordered structure of the protein.

Download

Share

COinS