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J. Biol. Chem., Vol. 283, Issue 24, 16573-16583, June 13, 2008

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Substrate Specificity and Membrane Topology of Escherichia coli PgpB, an Undecaprenyl Pyrophosphate Phosphatase^*

From the Université Paris-Sud, UMR 8619, Institut de Biochimie et Biophysique Moléculaire et Cellulaire and CNRS, Laboratoire des Enveloppes Bactériennes et Antibiotiques, UMR 8619, 91405 Orsay Cedex, France

The synthesis of the lipid carrier undecaprenyl phosphate (C₅₅-P) requires the dephosphorylation of its precursor, undecaprenyl pyrophosphate (C₅₅-PP). The latter lipid is synthesized de novo in the cytosol and is also regenerated after its release from the C₅₅-PP-linked glycans in the periplasm. In Escherichia coli the dephosphorylation of C₅₅-PP was shown to involve four integral membrane proteins, BacA, and three members of the type 2 phosphatidic acid phosphatase family, PgpB, YbjG, and YeiU. Here, the PgpB protein was purified to homogeneity, and its phosphatase activity was examined. This enzyme was shown to catalyze the dephosphorylation of C₅₅-PP with a relatively low efficiency compared with diacylglycerol pyrophosphate and farnesyl pyrophosphate (C₁₅-PP) lipid substrates. However, the in vitro C₅₅-PP phosphatase activity of PgpB was specifically enhanced by different phospholipids. We hypothesize that the phospholipids are important determinants to ensure proper conformation of the atypical long axis C₅₅ carrier lipid in membranes. Furthermore, a topological analysis demonstrated that PgpB contains six transmembrane segments, a large periplasmic loop, and the type 2 phosphatidic acid phosphatase signature residues at a periplasmic location.

Received for publication, January 16, 2008 , and in revised form, March 4, 2008.

^* This work was supported by grants from the European Community (FP6, COBRA project LSHM-CT-2003-503-335 and EUR-INTAFAR LSHM-CT-2004-512138) and from the CNRS (UMR 8619). 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 should be addressed: Laboratoire des Enveloppes Bactériennes et Antibiotiques, IBBMC, UMR8619 CNRS, Université Paris-Sud, Bâtiment 430, 91405 Orsay Cedex, France. Tel.: 33-1-69-15-61-34; Fax: 33-1-69-85-37-15; E-mail: thierry.touze{at}u-psud.fr.

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