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C-type Cytochromes (c-type + cytochrome)
Selected AbstractsLow-Temperature EPR and Mössbauer Spectroscopy of Two Cytochromes with His,Met Axial Coordination Exhibiting HALS Signals,CHEMPHYSCHEM, Issue 6 2006Giorgio Zoppellaro Dr. Abstract C-type cytochromes with histidine,methionine (His,Met) iron coordination play important roles in electron-transfer reactions and in enzymes. Low-temperature electron paramagnetic resonance (EPR) spectra of low-spin ferric cytochromes c can be divided into two groups, depending on the spread of g values: the normal rhombic ones with small g anisotropy and gmax below 3.2, and those featuring large g anisotropy with gmax between 3.3 and 3.8, also denoted as highly axial low spin (HALS) species. Herein we present the detailed magnetic properties of cytochrome c553 from Bacillus pasteurii (gmax 3.36) and cytochrome c552 from Nitrosomonas europaea (gmax 3.34) over the pH range 6.2 to 8.2. Besides being structurally very similar, cytochrome c553 shows the presence of a minor rhombic species at pH 6.2 (6,%), whereas cytochrome c552 has about 25,% rhombic species over pH 7.5. The detailed Mössbauer analysis of cytochrome c552 confirms the presence of these two low-spin ferric species (HALS and rhombic) together with an 8,% ferrous form with parameters comparable to the horse cytochrome c. Both EPR and Mössbauer data of axial cytochromes c with His,Met iron coordination are consistent with an electronic (dxy)2 (dxz)2 (dyz)1 ground state, which is typical for Type I model hemes. [source] Characterization of electrochemical activity of a strain ISO2-3 phylogenetically related to Aeromonas sp. isolated from a glucose-fed microbial fuel cellBIOTECHNOLOGY & BIOENGINEERING, Issue 5 2009Kyungmi Chung Abstract The microbial communities associated with electrodes in closed and open circuit microbial fuel cells (MFCs) fed with glucose were analyzed by 16S rRNA approach and compared. The comparison revealed that bacteria affiliated with the Aeromonas sp. within the Gammaproteobacteria constituted the major population in the closed circuit MFC (harvesting electricity) and considered to play important roles in current generation. We, therefore, attempted to isolate the dominant bacteria from the anode biofilm, successfully isolated a Fe (III)-reducing bacterium phylogenetically related to Aeromonas sp. and designated as strain ISO2-3. The isolated strain ISO2-3 could grow and concomitantly produce current (max. 0.24,A/m2) via oxidation of glucose or hydrogen with an electrode serving as the sole electron acceptor. The strain could ferment glucose, but generate less electrical current. Cyclic voltammetry supported the strain ISO2-3 was electrically active and likely to transfer electrons to the electrode though membrane-associated compounds (most likely c-type cytochrome). This mechanism requires intimate contact with the anode surface. Scanning electron microscopy revealed that the strain ISO2-3 developed multiplayer biofilms on the anode surface and also produced anchor-like filamentous appendages (most likely pili) that may promote long-range electron transport across the thick biofilm. Biotechnol. Bioeng. 2009; 104: 901,910. © 2009 Wiley Periodicals, Inc. [source] Cleavage of the iron-methionine bond in c-type cytochromes: Crystal structure of oxidized and reduced cytochrome c2 from Rhodopseudomonas palustris and its ammonia complexPROTEIN SCIENCE, Issue 1 2002Silvano Geremia Abstract The three-dimensional structures of the native cytochrome c2 from Rhodopseudomonas palustris and of its ammonia complex have been obtained at pH 4.4 and pH 8.5, respectively. The structure of the native form has been refined in the oxidized state at 1.70 Å and in the reduced state at 1.95 Å resolution. These are the first high-resolution crystal structures in both oxidation states of a cytochrome c2 with relatively high redox potential (+350 mV). The differences between the two oxidation states of the native form, including the position of internal water molecules, are small. The unusual six-residue insertion Gly82-Ala87, which precedes the heme binding Met93, forms an isolated 310 -helix secondary structural element not previously observed in other c-type cytochromes. Furthermore, this cytochrome shows an external methionine residue involved in a strained folding near the exposed edge of the heme. The structural comparison of the present cytochrome c2 with other c-type cytochromes has revealed that the presence of such a residue, with torsion angles , and , of approximately ,140 and ,130°, respectively, is a typical feature of this family of proteins. The refined crystal structure of the ammonia complex, obtained at 1.15 Å resolution, shows that the sulphur atom of the Met93 axial ligand does not coordinate the heme iron atom, but is replaced by an exogenous ammonia molecule. This is the only example so far reported of an X-ray structure with the heme iron coordinated by an ammonia molecule. The detachment of Met93 is accompanied by a very localized change in backbone conformation, involving mainly the residues Lys92, Met93, and Thr94. Previous studies under typical denaturing conditions, including high-pH values and the presence of exogenous ligands, have shown that the detachment of the Met axial ligand is a basic step in the folding/unfolding process of c-type cytochromes. The ammonia adduct represents a structural model for this important step of the unfolding pathway. Factors proposed to be important for the methionine dissociation are the strength of the H-bond between the Met93 and Tyr66 residues that stabilizes the native form, and the presence in this bacterial cytochrome c2 of the rare six-residue insertion in the helix 310 conformation that increases Met loop flexibility. [source] | ||||||||||