Biology subjects

Keenan, E. K.

Publications and source records attributed to Keenan, E. K..

2 recordsLinked to original sources

bioRxiv2024

Cysteine S-acetylation is a post-translational modification involved in metabolic regulation

Cysteine is a reactive amino acid central to the catalytic activities of many enzymes. It is also a common target of post-translational modifications (PTMs), such as palmitoylation. This long-chain acyl PTM can modify cysteine residues and induce changes in protein subcellular localization. We hypothesized that cysteine could also be modified by short-chain acyl groups, such as cysteine S-acetylation. To test this, we developed sample preparation and non-targeted mass spectrometry protocols to analyze the mouse liver proteome for cysteine acetylation. Our findings revealed hundreds of sites of cysteine acetylation across multiple tissue types, revealing a previously uncharacterized cysteine acetylome. Cysteine acetylation shows a marked cytoplasmic subcellular localization signature, with tissue-specific acetylome patterns and specific changes upon metabolic stress. This study uncovers a novel aspect of cysteine biochemistry, highlighting short-chain modifications alongside known long-chain acyl PTMs. These findings enrich our understanding of the landscape of acyl modifications and suggest new research directions in enzyme activity regulation and cellular signaling in metabolism.

biochemistry↗

bioRxiv2020

Structural basis for polyglutamate chain initiation and elongation by TTLL family enzymes

Glutamylation, introduced by TTLL enzymes, is the most abundant modification of brain tubulin. Essential effector proteins read the tubulin glutamylation pattern, and its misregulation causes neurodegeneration. TTLL glutamylases posttranslationally add glutamates to internal glutamates in tubulin C-terminal tails (branch initiation, through an isopeptide bond), and additional glutamates can extend these (elongation). TTLLs are thought to specialize for initiation or elongation, but the mechanistic basis for regioselectivity is unknown. We present cocrystal structures of murine TTLL6 bound to tetrahedral intermediate analogs that delineate key active-site residues that make this an elongase. We show that TTLL4 is exclusively an initiase, and through combined structural and phylogenetic analyses, engineer TTLL6 into a branch-initiating enzyme. TTLL glycylases add glycines posttranslationally to internal glutamates, and we find that the same active-site residues discriminate between initiase and elongase glycylases. These active-site specializations of TTLL glutamylases and glycylases ultimately yield the chemical complexity of cellular microtubules.

biochemistry↗