Structure, conformational stability, and enzymatic properties of acylphosphatase from the hyperthermophile Sulfolobus solfataricus

Alessandra Corazza, Camillo Rosano, Katiuscia Pagano, Vera Alverdi, Gennaro Esposito, Cristina Capanni, Francesco Bemporad, Georgia Plakoutsi, Massimo Stefani, Fabrizio Chiti, Simone Zuccotti, Martino Bolognesi, Paolo Viglino

Research output: Contribution to journalArticle

Abstract

The structure of AcP from the hyperthermophilic archaeon Sulfolobus solfataricus has been determined by 1H-NMR spectroscopy and X-ray crystallography. Solution and crystal structures (1.27 Å resolution, R-factor 13.7%) were obtained on the full-length protein and on an N-truncated form lacking the first 12 residues, respectively. The overall Sso AcP fold, starting at residue 13, displays the same βαββαβ topology previously described for other members of the AcP family from mesophilic sources. The unstructured N-terminal tail may be crucial for the unusual aggregation mechanism of Sso AcP previously reported. Sso AcP catalytic activity is reduced at room temperature but rises at its working temperature to values comparable to those displayed by its mesophilic counterparts at 25-37°C. Such a reduced activity can result from protein rigidity and from the active site stiffening due the presence of a salt bridge between the C-terminal carboxylate and the active site arginine. Sso AcP is characterized by a melting temperature, Tm, of 100.8°C and an unfolding free energy, ΔGU-FH2O, at 28°C and 81°C of 48.7 and 20.6 kJ mol-1, respectively. The kinetic and structural data indicate that mesophilic and hyperthermophilic AcP's display similar enzymatic activities and conformational stabilities at their working conditions. Structural analysis of the factor responsible for Sso AcP thermostability with respect to mesophilic AcP's revealed the importance of a ion pair network stabilizing particularly the β-sheet and the loop connecting the fourth and fifth strands, together with increased density packing, loop shortening and a higher α-helical propensity.

Original languageEnglish (US)
Pages (from-to)64-79
Number of pages16
JournalProteins: Structure, Function and Genetics
Volume62
Issue number1
DOIs
StatePublished - Jan 1 2006

Keywords

  • H NMM spectroscopy
  • Protein structure
  • Protein thermostability
  • Sulfolobus solfataricus acylphosphatase
  • X-ray crystallography

ASJC Scopus subject areas

  • Structural Biology
  • Biochemistry
  • Molecular Biology

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