Bifunctional structure of two adenylyl cyclases from the myxobacterium Stigmatella aurantiaca |
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Authors: | MP Coudart-Cavalli O Sismeiro A Danchin |
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Institution: | aDKFZ, Deutsches Krebs Forschung Zentrum, Im Neuenheimer Feld 280, 69120 Heidelberg, Germany;bInstitut Pasteur, Unité de Régulation de l'Expression Génétique, 28, rue du Docteur-Roux, 75724 Paris cedex 15, France |
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Abstract: | Two adenylyl cyclase genes (cyaA and cyaB) from the myxobacterium Stigmatella aurantiaca were cloned by complementation of Escherichia coli mutants defective in the cya gene. cyaA codes for a protein of 424 amino acid residues (AC1), while cyaB encodes a protein of 352 residues (AC2). Both cyclases are sensitive to adenosine: cAMP production was strongly inhibited in E coli cells and cell extracts expressing these genes. AC1 comprises a hydrophobic domain of six transmembrane helices coupled to a cytoplasmic catalytic domain endowed with adenylyl cyclase activity. A 17 amino acid residue sequence, which is a signature of G-protein coupled receptors, as well as of slime mold Dictyostelium discoideum cyclic AMP receptors, was found in the membrane domain. AC2 displays features also indicating that it is a bifunctional enzyme. The domain located upstream from the catalytic adenylyl cyclase domain shows strong similarity to receiver modules of response regulators of two-component bacterial signaling systems. In vitro mutagenesis of conserved aspartate residues in this domain was shown to interfere with cAMP synthesis. |
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Keywords: | two component regulatory systems multiple adenylyl cyclases bacterial differentiation cyclic nucleotides |
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