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The influence of a surface charge on the electronic and steric structure of a high potential iron-sulfur protein (1996)

Bertini, I. ; Borsari, Marco ; Bosi, Massimiliano ; [et al.]

Springer

JBIC 1 (1996), S. 257-263

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ISSN: 1432-1327

Keywords: Key words High-potential ; Iron-sulfur protein ; Redox ; Mutation

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Chemistry and Pharmacology

Notes: Abstract The recombinant high-potential iron-sulfur protein (HiPIP) iso-I from Ectothiorhodospira halophila has been mutated at position 68. The αC of Val 68 is within a 0.6-nm sphere from the closest iron ion of the cluster. The valine residue has been replaced by a negatively charged glutamate residue (V68E) and by a positively charged lysine residue (V68K). With respect to the recombinant wild-type protein the reduction potentials of the V68E and V68K variants are –21±2 and +29±2 mV respectively (200 mM NaCl, pH 7, 25 °C). The solution structure of the V68E mutant was solved up to a pairwise RMSD of 66 pm for backbone atoms and 138 pm for all heavy atoms. The structure of the variant is very similar to that of recombinant wild type, indicating that the observed changes in reduction potentials are largely due to the effect of the introduced charges. It is proposed that the valence distribution within the oxidized iron-sulfur cluster is affected only slightly by the change in charge at position 68, but consistently with a simple electrostatic model.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/s007750050051

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The Solution Structure of Oxidized HiPIP I from Ectothiorhodospira halophila; Can NMR Spectroscopy Be Used to Probe Rearrangements Associated with Electron Transfer Processes? (1995)

Bertini, Ivano ; Eltis, Lindsay D. ; Felli, Isabella C. ; [et al.]

Weinheim : Wiley-Blackwell

Chemistry - A European Journal 1 (1995), S. 598-607

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ISSN: 0947-6539

Keywords: electron transfer ; iron-sulfur proteins ; NMR spectroscopy ; proteins ; solution structures ; Chemistry ; General Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: In the 1H NMR spectrum of the oxidized form of the high-potential iron-sulfur protein (HiPIPI) from Ectothiorhodospira halophila, 91% of the total proton resonances and 100% of the residues have been assigned. The standard COSY, NOESY, and TOCSY sequences have been optimized for the paramagnetism of the molecule. Extensive assignment of the 15N NMR spectrum has been obtained through HMQC spectra. With 1437 dipolar connectivities, of which about 10% involved fast-relaxing protons, a family of 18 structures was generated with an RMSD of 0.65 Å by using the programs developed by Wüthrich. The family of structures was further refined by various calculation steps; the final RMSD was 0.48 Å. The structures appear to be very similar but not equal to the structures of the reduced protein. Despite the similarity in structure, significant variations in the chemical shifts are observed. A similar behavior was observed for the homologous protein from Chromatium vinosum. It is concluded that NMR is a sensitive tool to monitor differences between oxidized and reduced proteins; however, the detailed structural variations should be evaluated with caution at the present level of resolution, which roughly corresponds to a resolution of 2.5 Å in an X-ray structure.

Additional Material: 12 Ill.