Effect of Mutation of the Conservative Glycine Residues Gly100 and Gly147 on Stability of Escherichia coli Inorganic Pyrophosphatase

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V. M. Moiseev^1*, E. V. Rodina^1,2, and S. M. Avaeva²

¹Faculty of Chemistry, Lomonosov Moscow State University, 119992 Moscow, Russia; fax: (7-095) 932-8846; E-mail: mbutt@mail.ru

²Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, 119992 Moscow, Russia; fax: (7-095) 939-3181

^* To whom correspondence should be addressed.

Received February 28, 2004; Revision received November 26, 2004

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Sequence alignment of inorganic pyrophosphatases (PPases) isolated from the different organisms shows that glycine residues Gly100 and Gly147 are conservative. These residues are located in flexible segments of a polypeptide chain that have similar structure in the different PPases. To elucidate the possible role of these segments in the functioning of PPase, the mutant variants Gly100Ala and Gly147Val in conservative loops have been obtained. In this work, the influence of these mutations on stability of PPase globular structure has been studied. Differential scanning calorimetry has been used to determine the apparent enthalpy of thermal denaturation for the native PPase and its mutant variants Gly100Ala and Gly147Val. Guanidine hydrochloride-induced chemical denaturation of PPase has also been studied. It is shown that the substitutions of Gly100 and Gly147 result in overall destabilization of the globular structure.

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KEY WORDS: inorganic pyrophosphatase, globular structure, differential scanning calorimetry, chemical denaturation, energy of denaturation, stability

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