Mg2+ activation of Escherichia coli inorganic pyrophosphatase
- 11 December 1995
- journal article
- Published by Wiley in FEBS Letters
- Vol. 377 (1) , 44-46
- https://doi.org/10.1016/0014-5793(95)01310-5
Abstract
Further refinement of X-ray data on Escherichia coli inorganic pyrophosphatase [Oganessyan et al. (1994) FEBS Lett. 348, 301–304] to 2.2 Å reveals a system of noncovalent interactions involving Tyr55 and Tyr141 in the active site. The pKa for one of the eight Tyr residues in wild-type pyrophosphatase is as low as 9.1 and further decreases to 8.1 upon Mg2+ binding, generating characteristic changes in the absorption spectrum. These effects are lost in a Y55F but not in a Y141F variant. It is suggested that the lower-affinity site for Mg2+ in the enzyme is formed by Tyr55 and Asp70, which are in close proximity in the apo-enzyme structureKeywords
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