title: Spectroscopic analyses of manganese ions effects on the conformational changes of inorganic pyrophosphatase from psychrophilic Shewanella sp. AS-11.
abstract: Mn²⁺ ions influence the activity, temperature dependence, and thermostability of the psychrophilic Shewanella-PPase (Sh-PPase), and are required to function in cold environments. The functional characteristics of Sh-PPase on activation with Mn²⁺ ions are possibly related to conformational changes in the molecule. In this study, conformational changes of Sh-PPase on activation with Mn²⁺ ions were analyzed in solution by fluorescence spectroscopy analysis of intrinsic tryptophan residues, 1-anilino-8-naphthalene sulfonate fluorescence, and circular dichroism spectroscopy. For Sh-PPase, Mn²⁺ ions did not affect the flexibility of the tryptophan residues and secondary structure of the enzyme. However, the microenvironment of the tryptophan residues and surface area of Sh-PPase were more hydrophilic on activation with Mn²⁺ ions. These results indicate that activation with Mn²⁺ ions causes conformational changes around the aromatic amino acid residues and affects the hydrophobicity of the enzyme surface, which results in conformational changes. Substrate-induced conformational changes reflect that metal-free Sh-PPase in solution indicated an open structure and will be a close structure when binding substrate. In combination of our spectroscopic analyses on Sh-PPase, it can be concluded that activation with Mn²⁺ ions changes some conformation of Sh-PPase molecule in solution.
authors.affiliation: Department of Applied Biochemistry and Food Science, Saga University, 1-Honjo-machi, Saga, 840-8502, Japan, sn9073@edu.cc.saga-u.ac.jp.
authors.forename: Elvy Like
authors.initials: EL
authors.lastname: Ginting
authors.forename: Chihiro
authors.initials: C
authors.lastname: Maeganeku
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Motoshima
authors.forename: Keiichi
authors.initials: K
authors.lastname: Watanabe
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D043564:Inorganic Pyrophosphatase / Q000737:chemistry*; D007477:Ions / Q000737:chemistry*; D008345:Manganese / Q000737:chemistry*; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D020592:Shewanella / Q000737:chemistry / Q000201:enzymology
chemical_list: D007477:Ions; D008345:Manganese; D043564:Inorganic Pyrophosphatase