Comparative biochemical and functional studies of family I soluble inorganic pyrophosphatases from photosynthetic bacteria

Authors

  • María R. Gómez-García,

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    • Present address
      Department of Biochemistry, Stanford University School of Medicine, Beckman Center B413, Stanford, CA, USA

  • Manuel Losada,

    1. Instituto de Bioquímica Vegetal y Fotosíntesis, Centro de Investigaciones Científicas Isla Cartuja, CSIC-Universidad de Sevilla, Spain
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  • Aurelio Serrano

    1. Instituto de Bioquímica Vegetal y Fotosíntesis, Centro de Investigaciones Científicas Isla Cartuja, CSIC-Universidad de Sevilla, Spain
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M. R. Gómez-García, Department of Biochemistry, Stanford University School of Medicine, Beckman Center B413, 300 Pasteur Dr., Stanford, CA, 94305-5307, USA
Fax: +1 650 725 6044
Tel: +1 650 723 5348
E-mail: mrgomez@stanford.edu

A. Serrano, Instituto de Bioquímica Vegetal y Fotosíntesis, CSIC-Univ. de Sevilla, Avda. Américo Vespucio 49, 41092 - Sevilla, Spain Fax: +34 954460065 Tel: +34 954489524 E-mail: aurelio@ibvf.csic.es

Abstract

Soluble inorganic pyrophosphatases (inorganic diphosphatases, EC 3.6.1.1) were isolated and characterized from three phylogenetically diverse cyanobacteria − Synechocystis sp. PCC 6803, Anabaena sp. PCC 7120, and Pseudanabaena sp. PCC 6903 – and one anoxygenic photosynthetic bacterium, Rhodopseudomonas viridis (purple nonsulfur). These enzymes were found to be family I soluble inorganic pyrophosphatases with c. 20 kDa subunits with diverse oligomeric structures. The corresponding ppa genes were cloned and functionally validated by heterologous expression. Cyanobacterial family I soluble inorganic pyrophosphatases were strictly Mg2+-dependent enzymes. However, diverse cation cofactor dependence was observed for enzymes from other groups of photosynthetic bacteria. Immunochemical studies with antibodies to cyanobacterial soluble inorganic pyrophosphatases showed crossreaction with orthologs of other main groups of phototrophic prokaryotes and suggested a close relationship with the enzyme of heliobacteria, the nearest photosynthetic relatives of cyanobacteria. A slow-growing Escherichia coli JP5 mutant strain, containing a very low level of soluble inorganic pyrophosphatase activity, was functionally complemented up to wild-type growth rates with ppa genes from diverse photosynthetic prokaryotes expressed under their own promoters. Overall, these results suggest that the bacterial family I soluble inorganic pyrophosphatases described here have retained functional similarities despite their genealogies and their adaptations to diverse metabolic scenarios.

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