Date of Award
Fall 9-8-2025
Degree Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
Department
Chemistry
First Advisor
Miguel Ballicora
Abstract
Pyridoxal-5'-phosphate (PLP) is a versatile and evolutionarily conserved cofactor central to a wide array of metabolic processes, including amino acid metabolism, neurotransmitter regulation, and gene expression. This dissertation explores the diverse biochemical and structural roles of PLP across bacterial and human systems, providing insights into transcriptional regulation, enzymatic catalysis, and therapeutic targeting. The first portion of this work investigates the Bacillus subtilis (B. subtilis) GabR (bsGabR) protein, a GntR-type transcription factor that uniquely employs PLP to sense and respond to γ-aminobutyric acid (GABA) via an aminotransferase-like domain. X-ray crystallographic and spectroscopic analyses of Tyr281 mutants (Y281F, Y281L, Y281A) reveal how specific structural features suppress full transaminase activity, preserving GabR’s function as a signal-dependent transcriptional regulator. Further studies explore GabR’s potential as an antimicrobial target, leveraging its bacterial exclusivity. A synthetic PLP analog, pyridoxal-5'-tetrazole (PLT), and a GABA derivative (4-phenoxymethyl-GABA) were structurally characterized in complex with bsGabR, uncovering a stable external aldimine and introducing novel scaffolds for antibiotic development. The final section shifts focus to the Human GABA aminotransferase (hGABA-AT), a PLP-dependent enzyme critical in GABA metabolism. This work presents the first high-resolution structures of hGABA-AT in multiple mechanistic states, including its inactivation by the anticonvulsant OV329. These findings illuminate key catalytic features, such as the arginine switch mechanism, and support structure-based design of therapeutics for neurological disorders. Together, this dissertation underscores the biochemical versatility of PLP and its potential in modulating enzyme activity and guiding structure-informed drug discovery.
Recommended Citation
Kaley, Nicholas Eugene, "Structure, Function, and Therapeutic Potential of PLP-Dependent Macromolecules: Case Studies on Bacillus subtilis GabR and Human GABA Aminotransferase" (2025). Dissertations. 4238.
https://ecommons.luc.edu/luc_diss/4238
