2bq4

Crystal structure of type I cytochrome c3 from Desulfovibrio africanus

spinqualitylabelsall models 2bq4, resolution 1.68Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 2bq4 is a 2 chain structure with sequence from Desulfocurvibacter africanus. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Method: X-ray diffraction, Resolution 1.68Å Ligands: CA, HEC Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function CYC3B_DESAF Exchanges electrons with [NiFe] and [Fe] hydrogenases and with the acidic cytochrome c3. Participates in sulfate respiration coupled with phosphorylation by transferring electrons from the enzyme dehydrogenase to ferredoxin. Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMed In Desulfovibrio metabolism, periplasmic hydrogen oxidation is coupled to cytoplasmic sulfate reduction via transmembrane electron transfer complexes. Type II tetraheme cytochrome c3 (TpII-c3), nine-heme cytochrome c (9HcA) and 16-heme cytochrome c (HmcA) are periplasmic proteins associated to these membrane-bound redox complexes and exhibit analogous physiological function. Type I tetraheme cytochrome c3 (TpI-c3) is thought to act as a mediator for electron transfer from hydrogenase to these multihemic cytochromes. In the present work we have investigated Desulfovibrio africanus (Da) and Desulfovibrio vulgaris Hildenborough (DvH) TpI-c3/TpII-c3 complexes. Comparative kinetic experiments of Da TpI-c3 and TpII-c3 using electrochemistry confirm that TpI-c3 is much more efficient than TpII-c3 as an electron acceptor from hydrogenase (second order rate constant k = 9 x 10(8) M(-1) s(-1), K(m) = 0.5 microM as compared to k = 1.7 x 10(7) M(-1) s(-1), K(m) = 40 microM, for TpI-c3 and TpII-c3, respectively). The Da TpI-c3/TpII-c3 complex was characterized at low ionic strength by gel filtration, analytical ultracentrifugation and cross-linking experiments. The thermodynamic parameters were determined by isothermal calorimetry titrations. The formation of the complex is mainly driven by a positive entropy change (deltaS = 137(+/-7) J mol(-1) K(-1) and deltaH = 5.1(+/-1.3) kJ mol(-1)) and the value for the association constant is found to be (2.2(+/-0.5)) x 10(6) M(-1) at pH 5.5. Our thermodynamic results reveal that the net increase in enthalpy and entropy is dominantly produced by proton release in combination with water molecule exclusion. Electrostatic forces play an important role in stabilizing the complex between the two proteins, since no complex formation is detected at high ionic strength. The crystal structure of Da TpI-c3 has been solved at 1.5 angstroms resolution and structural models of the complex have been obtained by NMR and docking experiments. Similar experiments have been carried out on the DvH TpI-c3/TpII-c3 complex. In both complexes, heme IV of TpI-c3 faces heme I of TpII-c3 involving basic residues of TpI-c3 and acidic residues of TpII-c3. A secondary interacting site has been observed in the two complexes, involving heme II of Da TpII-c3 and heme III of DvH TpI-c3 giving rise to a TpI-c3/TpII-c3 molar ratio of 2:1 and 1:2 for Da and DvH complexes, respectively. The physiological significance of these alternative sites in multiheme cytochromes c is discussed. The type I/type II cytochrome c3 complex: an electron transfer link in the hydrogen-sulfate reduction pathway.,Pieulle L, Morelli X, Gallice P, Lojou E, Barbier P, Czjzek M, Bianco P, Guerlesquin F, Hatchikian EC J Mol Biol. 2005 Nov 18;354(1):73-90. Epub 2005 Sep 29. PMID:16226767 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See Also Cytochrome C 3D structures

Proteopedia Page Contributors and Editors (what is this?)

OCA