title: Molecular architecture of the human protein deacetylase Sirt1 and its regulation by AROS and resveratrol.
abstract: Sirtuins are NAD+-dependent protein deacetylases regulating metabolism, stress responses and ageing processes. Among the seven mammalian Sirtuins, Sirt1 is the physiologically best-studied isoform. It regulates nuclear functions such as chromatin remodelling and gene transcription, and it appears to mediate beneficial effects of a low calorie diet which can partly be mimicked by the Sirt1 activating polyphenol resveratrol. The molecular details of Sirt1 domain architecture and regulation, however, are little understood. It has a unique N-terminal domain and CTD (C-terminal domain) flanking a conserved Sirtuin catalytic core and these extensions are assumed to mediate Sirt1-specific features such as homo-oligomerization and activation by resveratrol. To analyse the architecture of human Sirt1 and functions of its N- and C-terminal extensions, we recombinantly produced Sirt1 and Sirt1 deletion constructs as well as the AROS (active regulator of Sirt1) protein. We then studied Sirt1 features such as molecular size, secondary structure and stimulation by small molecules and AROS. We find that Sirt1 is monomeric and has extended conformations in its flanking domains, likely disordered especially in the N-terminus, resulting in an increased hydrodynamic radius. Nevertheless, both termini increase Sirt1 deacetylase activity, indicating a regulatory function. We also find an unusual but defined conformation for AROS protein, which fails, however, to stimulate Sirt1. Resveratrol, in contrast, activates the Sirt1 catalytic core independent of the terminal domains, indicating a binding site within the catalytic core and suggesting that small molecule activators for other isoforms might also exist.
authors.affiliation: Department of Biochemistry, University of Bayreuth, Bayreuth, Germany.
authors.forename: Mahadevan
authors.initials: M
authors.lastname: Lakshminarasimhan
authors.forename: Ute
authors.initials: U
authors.lastname: Curth
authors.forename: Sebastien
authors.initials: S
authors.lastname: Moniot
authors.forename: Shyamal
authors.initials: S
authors.lastname: Mosalaganti
authors.forename: Stefan
authors.initials: S
authors.lastname: Raunser
authors.forename: Clemens
authors.initials: C
authors.lastname: Steegborn
mesh_terms: D000595:Amino Acid Sequence; D020134:Catalytic Domain / Q000187:drug effects; D003001:Cloning, Molecular; D000242:Cyclic AMP / Q000378:metabolism; D006152:Cyclic GMP / Q000378:metabolism; D006801:Humans; D009687:Nuclear Proteins / Q000737:chemistry / Q000378:metabolism*; D011487:Protein Conformation; D000077185:Resveratrol; D017384:Sequence Deletion; D056564:Sirtuin 1 / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D013267:Stilbenes / Q000494:pharmacology*; D014157:Transcription Factors / Q000737:chemistry / Q000378:metabolism*
chemical_list: D009687:Nuclear Proteins; C524448:RPS19BP1 protein, human; D013267:Stilbenes; D014157:Transcription Factors; D000242:Cyclic AMP; C447939:SIRT1 protein, human; D056564:Sirtuin 1; D006152:Cyclic GMP; D000077185:Resveratrol
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