Cloning,expression and physicochemical characterization of a di-heme cytochrome c4 from the psychrophilic bacterium Pseudoalteromonas haloplanktis TAC 125 |
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Authors: | Giulia Di Rocco Gianantonio Battistuzzi Marco Borsari Francesca De Rienzo Antonio Ranieri Maria Luisa Tutino Marco Sola |
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Affiliation: | Department of Chemistry, Università di Modena and Reggio Emilia, Via Campi 183, 41100, Modena, Italy. |
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Abstract: | The 20-kDa di-heme cytochrome c (4) from the psycrophilic bacterium Pseudoalteromonas haloplanktis TAC 125 was cloned and expressed in Escherichia coli and investigated through UV-vis and (1)H NMR spectroscopies and protein voltammetry. The model structure was computed using the X-ray structure of Pseudomonas stutzeri cytochrome c (4) as a template. The protein shows unprecedented properties within the cytochrome c (4) family, including (1) an almost nonpolar surface charge distribution, (2) the absence of high-spin heme Fe(III) states, indicative of a thermodynamically stable and kinetically inert axial heme His,Met coordination, and (3) identical E degrees ' values for the two heme centers (+0.322 V vs the standard hydrogen elecrode). At pH extremes, both heme groups undergo the "acid" and "alkaline" conformational transitions typical of class I cytochromes c, involving ligand-exchange equilibria, whereas at intermediate pH values their electronic properties are sensitive to several residue ionizations. |
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Keywords: | Cytochrome Electrochemistry Molecular modeling Electron transfer Voltammetry |
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