HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

J. Biol. Chem., Vol. 280, Issue 51, 41819-41826, December 23, 2005

This Article Full Text Full Text (PDF) All Versions of this Article: 280/51/41819    most recent M509489200v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Tammenkoski, M. Articles by Lahti, R. Search for Related Content PubMed PubMed Citation Articles by Tammenkoski, M. Articles by Lahti, R. Social Bookmarking                      What's this?

An Unusual, His-dependent Family I Pyrophosphatase from Mycobacterium tuberculosis^*

Marko Tammenkoski, Stefano Benini, Natalia N. Magretova¶, Alexander A. Baykov¶1, and Reijo Lahti2

From the Department of Biochemistry, University of Turku, FIN-20014 Turku, Finland, the University of York, Heslington, York YO10 5YW, United Kingdom, and the ^¶A. N. Belozersky Institute of Physico-Chemical Biology, Moscow State University, Moscow 119899, Russia

Soluble inorganic pyrophosphatases (PPases) comprise two evolutionarily unrelated families (I and II). These two families have different specificities for metal cofactors, which is thought to be because of the fact that family II PPases have three active site histidines, whereas family I PPases have none. Here, we report the structural and functional characterization of a unique family I PPase from Mycobacterium tuberculosis (mtPPase) that has two His residues (His²¹ and His⁸⁶) in the active site. The 1.3-Å three-dimensional structure of mtPPase shows that His⁸⁶ directly interacts with bound sulfate, which mimics the product phosphate. Otherwise, mtPPase is structurally very similar to the well studied family I hexameric PPase from Escherichia coli, although mtPPase lacks the intersubunit metal binding site found in E. coli PPase. The cofactor specificity of mtPPase resembles that of E. coli PPase in that it has high activity in the presence of Mg²⁺, but it differs from the E. coli enzyme and family II PPases because it has much lower activity in the presence of Mn²⁺ or Zn²⁺. Replacements of His²¹ and His⁸⁶ in mtPPase with the residues found in the corresponding positions of E. coli PPase had either no effect on the Mg²⁺- and Mn²⁺-supported reactions (H86K) or reduced Mg²⁺-supported activity (H21K). However, both replacements markedly increased the Zn²⁺-supported activity of mtPPase (up to 11-fold). In the double mutant, Zn²⁺ was a 2.5-fold better cofactor than Mg²⁺. These results show that the His residues in mtPPase are not essential for catalysis, although they determine cofactor specificity.

Received for publication, August 29, 2005 , and in revised form, October 7, 2005.

^* This work was supported by Academy of Finland Grant 201611, a grant for the National Graduate School in Informational and Structural Biology from the Ministry of Education and the Academy of Finland, European Community contract QLK2CT2001-02018 (Structural and functional genomics of M. tuberculosis), Russian Foundation for Basic Research Grant 03-04-48798, and Ministry of Industry, Science, and Technologies of the Russian Federation Grant 1706-2003-4. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

¹ To whom correspondence may be addressed. Tel.: 7-095-939-5541; Fax: 7-095-939-3181; E-mail: baykov{at}genebee.msu.su. ² To whom correspondence may be addressed. Tel.: 358-2-333-6845; Fax: 358-2-333-6860; E-mail: reijo.lahti{at}utu.fi.

CiteULike    Complore    Connotea    Del.icio.us    Digg    Reddit    Technorati    What's this?