Mg2+ activation of Escherichia coli inorganic pyrophosphatase

FEBS Letters

Avaeva, Svetlana M.³  Kurilova, Svetlana A.³  Nazarova, Tatjana I.³  Oganessyan, Vaheh Yu.¹  Harutyunyan, Emil H.¹  Rodina, Elena V.³  Vorobyeva, Natalja N.² 

[1] Institute of Crystallography, Russian Academy of Science, Moscow, Russian Federation;Department of Chemistry, Moscow State University, Moscow 119899, Russian Federation;A.N. Belozersky Institute of Physico-Chemical Biology, Moscow State University, Vorobyevy Gory, Moscow 119899, Russian Federation

关键词: Inorganic pyrophosphatase;    Tyrosine;    Mg2+ binding;    Differential spectrophotometry;    X-ray analysis;   

DOI  :  10.1016/0014-5793(95)01310-5

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

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 pK_a 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.

【 授权许可】

Unknown