Date Approved

2015

Graduate Degree Type

Thesis

Degree Name

Cell and Molecular Biology (M.S.)

Degree Program

Cell and Molecular Biology

First Advisor

Matthew Christians

Second Advisor

Sheila Blackman

Third Advisor

Agnieszka Szarecka

Abstract

The conjugation of the NEDD8 protein has been found to cause a wide range of changes to the overall function of a protein. The addition of NEDD8 to a conserved lysine on Cul proteins has been found to provide Cul with increased flexibility, while the transcription factor protein p53 was prevented from binding to DNA after NEDD8 conjugation. Using Arabidopsis thaliana, we investigated the potential conjugation of NEDD8 to the AtLRB1 and AtLRB2 proteins, which are both members of Cul3-RING E3 Ubiquitin Ligase complexes, using both in vitro and in silico techniques. The AtLRBs are negative regulators of the red light response pathway, interacting preferentially with Cul3 in red light conditions by an unknown mechanism.

Our investigation into the amino-terminal portion of AtLRB2 (residues 1-144) found two conserved regions which contained high sequence identity with Cul1 and Rbx1, two members of Cullin-RING ligase complexes. These two conserved regions were also found to share a similar distribution and placement on both the native crystal structure of Cullin proteins in complex with Rbx1 and on the predicted AtLRB2 structural protein model. Furthermore, the region of Rbx1 sharing sequence similarity to the LRBs directly interacts with NEDD8. Preliminary in vitro results also suggest that purified AtLRB2 is modified by NEDD8, but the significance of this modification on the function of the LRB proteins is not yet known.

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