title: Cloning, expression and physicochemical characterization of a di-heme cytochrome c (4) from the psychrophilic bacterium Pseudoalteromonas haloplanktis TAC 125.
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.
authors.affiliation: Department of Chemistry, Università di Modena and Reggio Emilia, Via Campi 183, 41100, Modena, Italy.
authors.forename: Giulia
authors.initials: G
authors.lastname: Di Rocco
authors.forename: Gianantonio
authors.initials: G
authors.lastname: Battistuzzi
authors.forename: Marco
authors.initials: M
authors.lastname: Borsari
authors.forename: Francesca
authors.initials: F
authors.lastname: De Rienzo
authors.forename: Antonio
authors.initials: A
authors.lastname: Ranieri
authors.forename: Maria Luisa
authors.initials: ML
authors.lastname: Tutino
authors.forename: Marco
authors.initials: M
authors.lastname: Sola
mesh_terms: D000136:Acid-Base Equilibrium; D000595:Amino Acid Sequence; D015374:Biosensing Techniques; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D003001:Cloning, Molecular; D004563:Electrochemistry; D015971:Gene Expression Regulation, Enzymologic; D005798:Genes, Bacterial; D006863:Hydrogen-Ion Concentration; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000096:biosynthesis / Q000737:chemistry* / Q000235:genetics*; D011487:Protein Conformation; D031161:Pseudoalteromonas / Q000201:enzymology* / Q000235:genetics*; D013056:Spectrophotometry, Ultraviolet; D013329:Structure-Activity Relationship
chemical_list: D010088:Oxidoreductases; C090099:diheme cytochrome c