Role of polar and nonpolar residues at the active site for PPIase activity of FKBP22 from Shewanella sp. SIB1

Authors

  • Cahyo Budiman,

    1.  Department of Material and Life Science, Graduate School of Engineering, Osaka University, Japan
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    • Present address
      Department of Animal Production and Technology, Faculty of Animal Science, Bogor Agricultural University (IPB), Indonesia

  • Takashi Tadokoro,

    1.  Department of Material and Life Science, Graduate School of Engineering, Osaka University, Japan
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  • Clement Angkawidjaja,

    1.  Department of Material and Life Science, Graduate School of Engineering, Osaka University, Japan
    2.  International College, Osaka University, Japan
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  • Yuichi Koga,

    1.  Department of Material and Life Science, Graduate School of Engineering, Osaka University, Japan
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  • Shigenori Kanaya

    1.  Department of Material and Life Science, Graduate School of Engineering, Osaka University, Japan
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S. Kanaya, Department of Material and Life Science, Graduate School of Engineering, Osaka University, 2-1, Yamadaoka, Suita, Osaka 565-0871, Japan
Fax: +81 6 6879 7938
Tel: +81 6 6879 7938
E-mail: kanaya@mls.eng.osaka-u.ac.jp

Abstract

FKBP22 from the psychotropic bacterium Shewanella sp. SIB1 is a homodimeric protein with peptidyl prolyl cis–trans isomerase (PPIase) activity. According to a tertiary model, several nonpolar residues including Trp157 and Phe197 form a substrate-binding cavity, and Asp137 and Arg142, which form a salt bridge, are located at the edge of this cavity. To analyze the role of these residues, nine single (D137A, R142A, W157A/F/Y, F197A/L/Y/W) and one double (D137A/R142A) mutant protein of SIB1 FKBP22 were constructed. The far- and near-UV CD spectra of these mutant proteins suggest that the mutations at Asp137 and Arg142 do not seriously affect the protein structure, while those at Trp157 and Phe197 cause a local conformational change around the mutation site. Each mutation decreased the PPIase activities of SIB1 FKBP22 for peptide and protein substrates similarly without seriously affecting chaperone function. This result indicates that SIB1 FKBP22 does not require PPIase activity for chaperone function. The PPIase activities of R142A, D137A and D137A/R142A decreased in this order, suggesting that Asp137 and Arg142 play a principal and auxiliary role in catalytic function, respectively, but Arg142 can function as a substitute of Asp137. Because the PPIase activity of SIB1 FKBP22 was not fully lost by the removal of all polar residues around the active site, the desolvation effect may also contribute to the enzymatic activity. However, the mutations of Trp157 to Phe or Phe197 to Leu greatly decrease the enzymatic activity, suggesting that the shape of the substrate-binding cavity is also important for enzymatic activity.

Database

Peptidyl prolyl cis–trans isomerase (PPIase, EC5.2.1.8)

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