Structural highlights
Publication Abstract from PubMedCatalytically inactive enzyme paralogs occur in many genomes. Some regulate their active counterparts but the structural principles of this regulation remain largely unknown. We report X-ray structures of Trypanosoma brucei S-adenosylmethionine decarboxylase alone and in functional complex with its catalytically dead paralogous partner, prozyme. We show monomeric TbAdoMetDC is inactive because of autoinhibition by its N-terminal sequence. Heterodimerization with prozyme displaces this sequence from the active site through a complex mechanism involving a cis-to-trans proline isomerization, reorganization of a beta-sheet, and insertion of the N-terminal alpha-helix into the heterodimer interface, leading to enzyme activation. We propose that the evolution of this intricate regulatory mechanism was facilitated by the acquisition of the dimerization domain, a single step that can in principle account for the divergence of regulatory schemes in the AdoMetDC enzyme family. These studies elucidate an allosteric mechanism in an enzyme and a plausible scheme by which such complex cooperativity evolved. Relief of autoinhibition by conformational switch explains enzyme activation by a catalytically dead paralog.,Volkov OA, Kinch L, Ariagno C, Deng X, Zhong S, Grishin N, Tomchick DR, Chen Z, Phillips MA Elife. 2016 Dec 15;5. pii: e20198. doi: 10.7554/eLife.20198. PMID:27977001[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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