Mg2+ activation of Escherichia coli inorganic pyrophosphatase.
Further refinement of X-ray data on Escherichia coli inorganic pyrophosphatase [Oganessyan et al. (1994) FEBS Lett. 348, 301-304] to 2.2 A 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 structure.
A.N. Belozersky Institute of Physico-Chemical Biology, Moscow State University, Russian Federation.
S M
SM
Avaeva
E V
EV
Rodina
S A
SA
Kurilova
T I
TI
Nazarova
N N
NN
Vorobyeva
E H
EH
Harutyunyan
Oganessyan VYu
D001665:Binding Sites; D018360:Crystallography, X-Ray; D004789:Enzyme Activation / Q000187:drug effects; D004926:Escherichia coli / Q000201:enzymology*; D006863:Hydrogen-Ion Concentration; D043564:Inorganic Pyrophosphatase; D008274:Magnesium / Q000378:metabolism / Q000494:pharmacology*; D015394:Molecular Structure; D011755:Pyrophosphatases / Q000737:chemistry / Q000378:metabolism*; D011994:Recombinant Proteins; D013053:Spectrophotometry; D014443:Tyrosine / Q000737:chemistry
D011994:Recombinant Proteins; D014443:Tyrosine; D011755:Pyrophosphatases; D043564:Inorganic Pyrophosphatase; D008274:Magnesium