Structural Studies of Metal Ions in Family II Pyrophosphatases: The Requirement for a Janus Ion

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• 作者：Igor P. Fabrichniy ; Lari Lehtiö ; Anu Salminen ; Anton B. Zyryanov ; Alexander A. Baykov ; Reijo Lahti ; and Adrian Goldman
• 刊名：Biochemistry
• 出版年：2004
• 出版时间：November 16, 2004
• 年：2004
• 卷：43
• 期：45
• 页码：14403 - 14411
• 全文大小：578K
• 年卷期：v.43,no.45(November 16, 2004)
• ISSN：1520-4995

文摘

Family II inorganic pyrophosphatases (PPases) constitute a new evolutionary group of PPases,with a different fold and mechanism than the common family I enzyme; they are related to the "DHH"family of phosphoesterases. Biochemical studies have shown that Mn²⁺ and Co²⁺ preferentially activatefamily II PPases; Mg²⁺ partially activates; and Zn²⁺ can either activate or inhibit (Zyryanov et al.,Biochemistry, 43, 14395-14402, accompanying paper in this issue). The three solved family II PPasestructures did not explain the differences between the PPase families nor the metal ion differences describedabove. We therefore solved three new family II PPase structures: Bacillus subtilis PPase (Bs-PPase)dimer core bound to Mn²⁺ at 1.3 Å resolution, and, at 2.05 Å resolution, metal-free Bs-PPase andStreptococcus gordonii (Sg-PPase) containing sulfate and Zn²⁺. Comparison of the new and old structuresof various family II PPases demonstrates why the family II enzyme prefers Mn²⁺ or Co²⁺, as an activatorrather than Mg²⁺. Both M1 and M2 undergo significant changes upon substrate binding, changing fromfive-coordinate to octahedral geometry. Mn²⁺ and Co²⁺, which readily adopt different coordination statesand geometries, are thus favored. Combining our structures with biochemical data, we identified M2 asthe high-affinity metal site. Zn²⁺ activates in the M1 site, where octahedral geometry is not essential forcatalysis, but inhibits in the M2 site, because it is unable to assume octahedral geometry but remainstrigonal bipyramidal. Finally, we propose that Lys205-Gln81-Gln80 form a hydrophilic channel to speedproduct release from the active site.