| Autor: |
Cioni, Patrizia, Piras, Luciana, Strambini, Giovanni Battista |
| Předmět: |
|
| Zdroj: |
European Journal of Biochemistry; 11/20/89, Vol. 185 Issue 3, p573-579, 7p |
| Abstrakt: |
The phosphorescence properties of Trp109 in alkaline phosphatase from Escherichia coli have been utilized to probe the conformation of the polypeptide following the removal of metal ions, reconstitution with Zn2+ and Cd2+ and phosphorylation. The complete removal of metal ions induces a drastic loosening of the protein structure that extends to the inner core of the macromolecule. While binding of a single metal ion/subunit (A-site occupancy) restores the holoconformer, practically no structuring effect is observed upon B-site occupancy by the second incoming metal ion. An exception to this rule occurs at alkaline pH and when the adjacent subunit in the dimer is metal-free. Under these circumstances a conformation of the subunit more compact than that of the fully saturated dimer manifests some degree of communication across the subunit interface. The binding of more than two metal ions/monomer generally destabilizes the protein, the effect being more pronounced at acid pH. Finally, the binding of inorganic phosphate restores the native-like configuration abolishing any destabilization induced by excess metal ions and acid pH. If the negative cooperativity towards metal binding to A sites in doubly metalated forms at pH 8 is in substantial agreement with 113Cd-NMR data, the equivalence in conformation between Zn2+- and Cd2+-reconstituted alkaline phosphatase emphasizes that no serious structural changes are introduced by the metal replacement. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
| Externí odkaz: |
|
