| Autor: |
Harmony, Judith A.K., Shaffer, Phyllis J., Himes, Richard H. |
| Zdroj: |
Journal of Biological Chemistry; January 1974, Vol. 249 Issue: 2 p394-401, 8p |
| Abstrakt: |
Formyltetrahydrofolate synthetase purified from Clostridium cylindrosporumand Clostridium acidi-uriciexists as a catalytically active tetramer in the presence of specific monovalent cations or as an inactive monomer in their absence. Addition of monovalent cations to the dissociated enzyme causes the monomers to reassociate to the tetramer. The order of cation effectiveness is NH4+> T1+> Rb+∼ K+> Cs+> Na+∼ Li+. The rate and the extent of reactivation is influenced by the counter ion. Sulfate and phosphate, for example, stimulate reassociation while thiocyanate, trichloroacetate, and perchlorate completely inhibit the reaction. This effect is attributed to the ability of the anion to alter the “iceberg” structure of water which exists about exposed hydrophobic residues on the monomer. Increasing the ionic strength of the reaction medium results in an increase in both the rate and the extent of reassociation. Difference spectroscopy experiments suggest that aromatic amino acids are buried during reassociation. |
| Databáze: |
Supplemental Index |
| Externí odkaz: |
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