Abstract 2119 Structural and Mechanistic Analysis of Ca2+ Dependent Regulation of Transglutaminase 2 Activity
Year: 2024
Type: conference-abstract
Abstract: Mammalian transglutaminases, a family of Ca2+ dependent proteins, are implicated in a variety of diseases. For example, celiac disease is an autoimmune disorder whose pathogenesis requires Transglutaminase 2 (TG2) to deamidate selected glutamine residues in diet-derived gluten peptides. Deamidation involves the formation of transient ϒ-glutamylthioester intermediates. Recent studies have revealed that, in addition to deamidated gluten peptides themselves, the corresponding thioester intermediates are also pathogenically relevant, although a mechanistic understanding of this relevance is hindered by the absence of any structure of Ca2+-bound TG2. We report the X-ray crystallographic structure of human TG2 bound to an inhibitory gluten peptidomimetic and two calcium ions in sites previously designated as S1 and S3. Site-directed mutagenesis confirmed that S1 regulates the formation of an inhibitory disulfide bond while also establishing that S3 is solely responsible for forming and resolving the ϒ-glutamylthioester intermediate. Further structure-based mutagenesis also demonstrated that two interacting residues, H305 and E363, play a critical role in resolving the thioester intermediate into an isopeptide bond (transamidation) but not thioester hydrolysis (deamidation). Together, our findings lead us to conclude that, although TG2 can bind to Ca2+ ions at least five allosteric sites, only one of them (S3) is necessary for both halves of the catalytic cycle.
Source: Journal of Biological Chemistry
Institution: Stanford University
Language: English
Subfield: Gastroenterology
Field: Medicine
Domain: Health Sciences
Open Access status: gold
Estimated APC paid: $2,800
OpenAlex ID: W4393138957