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Publication Abstract from PubMed

Methionine S-adenosyltransferases (MATs) are predominantly homotetramers, comprised of dimers of dimers. The larger, highly conserved intradimeric interface harbors two active sites, making the dimer the obligatory functional unit. However, functionality of the smaller, more diverged, and recently evolved interdimeric interface is largely unknown. Here, we show that the interdimeric interface of Ureaplasmaurealiticum MAT has evolved to control the catalytic activity and structural integrity of the homotetramer in response to product accumulation. When all four active sites are occupied with the product, S-adenosylmethionine (SAM), binding of four additional SAM molecules to the interdimeric interface prompts a approximately 45 degrees shift in the dimer orientation and a concomitant approximately 60% increase in the interface area. This rearrangement inhibits the enzymatic activity by locking the flexible active site loops in a closed state and renders the tetramer resistant to proteolytic degradation. Our findings suggest that the interdimeric interface of MATs is subject to rapid evolutionary changes that tailor the molecular properties of the entire homotetramer to the specific needs of the organism.

The interdimeric interface controls function and stability of Ureaplasma urealiticum methionine S-adenosyltransferase.,Kleiner D, Shmulevich F, Zarivach R, Shahar A, Sharon M, Ben-Nissan G, Bershtein S J Mol Biol. 2019 Dec 6;431(24):4796-4816. doi: 10.1016/j.jmb.2019.09.003. Epub, 2019 Sep 12. PMID:31520601^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.