Search

Mn 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 Mn ions are possibly related to conformational changes in the molecule. In this study, conformational changes of Sh-PPase on activation with Mn 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, Mn 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 Mn ions. These results indicate that activation with Mn 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 Mn ions changes some conformation of Sh-PPase molecule in solution. [ABSTRACT FROM AUTHOR]