Invited speaker: Rachel Ogorzalek Loo, Ph.D.

Chemistry and Biochemistry, UCLA-DOE Institute for Genomics and Proteomics, University of California-Los Angeles

Title: The Dynamic Acylome Reveals Metabolite-Driven Modifications in Syntrophic Microbes

Abstract

Syntrophomonas wolfei and Syntrophus aciditrophicus are anaerobic syntrophic microbes that degrade short-chain fatty acids to acetate, hydrogen, and/or formate. This thermodynamically unfavorable process proceeds through a series of reactive acyl-Coenzyme A species (RACS). In other prokaryotic and eukaryotic systems, the production of intrinsically reactive metabolites correlates with acyl-lysine modifications, which have been shown to play a significant role in metabolic processes. Analogous studies with syntrophic bacteria, however, were relatively unexplored, and we hypothesized that highly abundant acylations could exist in their proteins, corresponding to the RACS derived from degrading fatty acids. By mass spectrometry-based proteomics (LC– MS/MS), we characterized and compared acylome profiles of organisms cultivated with different carbon substrates. Because modified proteins are sufficiently abundant in these organisms to analyze post-translational modifications (PTMs) without antibody enrichment, we could identify acylations comprehensively, observing six types (acetyl-, butyryl-, 3-hydroxybutyryl-, crotonyl-, valeryl-, and hexanyl-lysine). All the acyl-PTMs identified correspond directly to RACS in fatty acid degradation pathways. A total of 369 sites of modification were identified on 237 proteins. Structural studies and in vitro acylation assays of a heavily modified enzyme, acetyl-CoA transferase, provided insight on the potential impact of these acyl-protein modifications. The extensive changes in acylation-type, abundance, and modification sites with carbon substrate suggest that protein acylation by RACS may be an important regulator of syntrophy.

Sponsored by the Department of Chemistry, Biochemistry, and Biomolecular Sciences Institute.