Graduation Year

2016

Document Type

Dissertation

Degree

Ph.D.

Degree Name

Doctor of Philosophy (Ph.D.)

Degree Granting Department

Medical Sciences

Major Professor

Robert Deschenes, Ph.D.

Co-Major Professor

Vladimir Uversky, Ph.D., D.Sc.

Committee Member

Yu Chen, Ph.D.

Committee Member

Gloria Ferreira, Ph.D.

Committee Member

Sameer Varma, Ph.D.

Committee Member

Walter Schmidt, Ph.D.

Keywords

Acylation, Protein Acyltransferase, Intrinsically Disordered Protein, Fatty Acid Metabolism, Palmitoylation Predictor, X-Linked Intellectual Disability

Abstract

Protein palmitoylation refers to the process of adding a 16-carbon saturated fatty acid to the cysteine of a substrate protein, and this can in turn affect the substrate’s localization, stability, folding, and several other processes. This process is catalyzed by a family of 23 mammalian protein acyltransferases (PATs), a family of transmembrane enzymes that modify an estimated 10% of the proteome. At this point in time, no structure of a protein in this family has been solved, and therefore there is poor understanding about the regulation of the enzymes and their substrates. Most proteins, including palmitoylation enzymes and substrates, have some level of intrinsic disorder, and this flexibility can be important for signaling processes such as protein- protein interactions and post-translational modifications. Therefore, we assumed that examining intrinsic disorder in palmitoylation enzymes and substrates would yield insight into their regulatory mechanisms. First, we found that among other factors, utilizing intrinsic disorder predictions led to a palmitoylation predictor that significantly outperformed existing predictors. Next, we discovered a conserved region of predicted disorder-to-order transition in the disordered C-termini of the PAT family. In Erf2, the yeast Ras PAT, we developed a model where this region reversibly interacts with membranes, and we found that this region mediates interaction with Acc1, an enzyme involved in fatty acid metabolism processes. Finally, we found that an XLID-associated nonsense mutation in zDHHC9, the mammalian Ras PAT, removed a disordered region that was critical for enzyme localization. Future studies of palmitoylation utilizing the framework of intrinsic disorder may lead to additional insights about this important regulatory process.

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