title: Post-translational S-nitrosylation is an endogenous factor fine tuning the properties of human S100A1 protein.
abstract: BACKGROUND
  S100A1 protein is a proposed target of molecule-guided therapy for heart failure.
  
  
  RESULTS
  S-Nitrosylation of S100A1 is present in cells, increases Ca(2+) binding, and tunes the overall protein conformation.
  
  
  CONCLUSIONS
  Thiol-aromatic molecular switch is responsible for NO-related modification of S100A1 properties.
  
  
  CONCLUSIONS
  Post-translational S-nitrosylation may provide functional diversity and specificity to S100A1 and other S100 protein family members. S100A1 is a member of the Ca(2+)-binding S100 protein family. It is expressed in brain and heart tissue, where it plays a crucial role as a modulator of Ca(2+) homeostasis, energy metabolism, neurotransmitter release, and contractile performance. Biological effects of S100A1 have been attributed to its direct interaction with a variety of target proteins. The (patho)physiological relevance of S100A1 makes it an important molecular target for future therapeutic intervention. S-Nitrosylation is a post-translational modification of proteins, which plays a role in cellular signal transduction under physiological and pathological conditions. In this study, we confirmed that S100A1 protein is endogenously modified by Cys(85) S-nitrosylation in PC12 cells, which are a well established model system for studying S100A1 function. We used isothermal calorimetry to show that S-nitrosylation facilitates the formation of Ca(2+)-loaded S100A1 at physiological ionic strength conditions. To establish the unique influence of the S-nitroso group, our study describes high resolution three-dimensional structures of human apo-S100A1 protein with the Cys(85) thiol group in reduced and S-nitrosylated states. Solution structures of the proteins are based on NMR data obtained at physiological ionic strength. Comparative analysis shows that S-nitrosylation fine tunes the overall architecture of S100A1 protein. Although the typical S100 protein intersubunit four-helix bundle is conserved upon S-nitrosylation, the conformation of S100A1 protein is reorganized at the sites most important for target recognition (i.e. the C-terminal helix and the linker connecting two EF-hand domains). In summary, this study discloses cysteine S-nitrosylation as a new factor responsible for increasing functional diversity of S100A1 and helps explain the role of S100A1 as a Ca(2+) signal transmitter sensitive to NO/redox equilibrium within cells.
authors.affiliation: National Institute of Chemistry, Slovenian NMR Centre, Hajdrihova 19, 1001 Ljubljana, Slovenia.
authors.forename: Martina
authors.initials: M
authors.lastname: Lenarčič Živković
authors.forename: Monika
authors.initials: M
authors.lastname: Zaręba-Kozioł
authors.forename: Liliya
authors.initials: L
authors.lastname: Zhukova
authors.forename: Jarosław
authors.initials: J
authors.lastname: Poznański
authors.forename: Igor
authors.initials: I
authors.lastname: Zhukov
authors.forename: Aleksandra
authors.initials: A
authors.lastname: Wysłouch-Cieszyńska
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D002460:Cell Line; D006801:Humans; D007700:Kinetics; D009569:Nitric Oxide / Q000378:metabolism*; D016716:PC12 Cells; D011485:Protein Binding; D011499:Protein Processing, Post-Translational; D017433:Protein Structure, Secondary; D051381:Rats; D009418:S100 Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D009418:S100 Proteins; C110294:S100A1 protein; D009569:Nitric Oxide; D002118:Calcium