Structural and Functional Characterization of the Human Tribbles Homologue 2 Pseudokinase
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Authors
Hicks, Gregory
Date
2016-10-27
Type
thesis
Language
eng
Keyword
pseudokinase , protein kinases , nucleotide binding , biochemistry , kinase activity , protein expression , tribbles homologue , protein purification , Trb2
Alternative Title
Abstract
The Tribbles Homologues are a family of three eukaryotic pseudokinases (Trb1, Trb2, Trb3) that act as allosteric inhibitors and regulatory scaffold sites in pathways governing adipogenesis, cell proliferation and insulin signaling. The Tribbles Homologues have the same overall tertiary structure of the eukaryotic protein kinase domain, but lack multiple residues necessary to catalysis in the nucleotide-binding P-loop and the Mg2+-coordinating DFG motif. Trb1 has been shown conclusively to be incapable of binding ATP, whereas a recent study presents evidence that Trb2 autophosphorylates independently of Mg2+ in vitro. This finding is surprising given the high degree of sequence similarity between the two proteins (71%), and suggests unique nucleotide binding and phosphotransfer mechanisms. The goal of this project was to investigate whether Trb2 possesses kinase activity or not and determine its structural basis. A method for the high-yield recombinant expression and purification of stable Trb2 was developed. Trb2 nucleotide binding and autophosphorylation could not be detected across multiple experimental approaches, including thermal shift assays, MANT-ATP fluorescence, radiolabeled phosphate incorporation, and nonspecific ATPase activity assays. Further characterization also revealed that Trb2 forms homomultimers with possible functional consequences, and extensive crystallization screening has yielded multiple promising conditions that could produce diffraction-quality crystals with further optimization. This project explores the difficulties in functionally characterizing putatively active pseudokinases, and proposes a structural basis for the conserved pseudokinase features of the Tribbles homologues.
Description
Thesis (Master, Biochemistry) -- Queen's University, 2016-10-26 16:12:40.655
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ProQuest PhD and Master's Theses International Dissemination Agreement
Intellectual Property Guidelines at Queen's University
Copying and Preserving Your Thesis
Creative Commons - Attribution - CC BY
This publication is made available by the authority of the copyright owner solely for the purpose of private study and research and may not be copied or reproduced except as permitted by the copyright laws without written authority from the copyright owner.