Regulation of Fatty Acid Biosynthesis by Protein Phosphorylation of the α-CT Subunit of ACCase in Arabidopsis thaliana
Date
2024-04-30
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Abstract
Reversible protein phosphorylation, the most common post-translational modification, is essential in mediating most cellular functions in living organisms. With recent advances in omics-based technologies and its applications to studying the phosphoproteome of particular organisms, many previously uncharacterized phosphoproteins, protein kinases and protein phosphatases have been identified. Shewanella-like protein phophatase 1 (SLP1), a novel Arabidopsis thaliana protein phosphatase localized to the chloroplast, is a protein of interest as it is predicted to play an antagonistic role to the constitutively active chloroplast localized kinase, casein kinase 2α4 (CK2α4). Through a quantitative mass spectrometry based phosphoproteomics study carried out by previous members of the Moorhead Lab, many putative substrates of AtSLP1 were identified, one of them being the alpha-carboxyltransferase (α-CT) subunit of heteromeric acetyl-CoA carboxylase (htACCase). HtACCase catalyzes the first committed step of de novo fatty acid biosynthesis, and like AtSLP1, is chloroplast localized. HtACCase has been known to interact with the chloroplast envelope membrane through association with an integral membrane protein, however, the identity of this protein has been a mystery until recently. Carboxyltransferase interactors (CTIs), a group of small plastidal proteins of the inner chloroplast envelope have been identified to interact with the α-CT subunit of htACCase in a light-dependent manner. The focus of the research presented here was to characterize α-CT as a substrate of both CK2α4 and SLP1 and to determine the role of protein phosphorylation in lipid metabolism. Here, initial steps were taken in employing phosphospecific antibodies against the S741 site on α-CT, with immunoblot analysis confirming previous findings from a phosphoproteomics study indicating hyperphosphorylation of α-CT in the absence of SLP1. To explore the relationship between protein phosphorylation and the membrane partitioning of ACCase with CTI, recombinant proteins were cloned for subsequent protein-protein interaction studies. By studying the effects of this post-translational modification, we will gain a better understanding of the role of protein phosphorylation in regulating fatty acid biosynthesis, which will ultimately uncover new ways to increase bio-oil production in crops.
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Keywords
Post-translational modification, Protein phosphorylation, Lipid Metabolism, SLP1
Citation
Wong, L. (2024). Regulation of fatty acid biosynthesis by protein phosphorylation of the α-CT subunit of ACCase in Arabidopsis thaliana (Master's thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.