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  • protein dynamics  (2)
  • Key words High-potential  (1)
  • Mutation  (1)
  • Redox  (1)
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  • 1
    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 The valine residue has been replaced by a negatively charged glutamate residue (V68E) and by a positively charged lysine residue (V68K).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
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  • 2
    ISSN: 1573-5001
    Keywords: protein dynamics ; nitrogen-15 NMR ; rotating-frame relaxation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Rotating-frame 15N relaxation rate (R1ρ) NMR experiments have been performed in order to study the dynamic behavior of the reduced recombinant high-potential iron-sulfur protein iso I (HiPIP I) from Ectothiorhodospira halophila, in the μs to ms time range. Measurements of R1ρ were performed as a function of the effective spin-lock magnetic field amplitude by using both on and off-resonance radio frequency irradiation. The two data sets provided consistent results and were fit globally in order to identify possible exchange processes in an external loop of the reduced HiPIP I. The loop consists of residues 43-45 and the correlation time of the exchange process was determined to be 50 ± 8 μs for the backbone nitrogen of Gln 44.
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  • 3
    ISSN: 1573-5001
    Keywords: cross-correlation ; protein dynamics ; spin diffusion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The mobility of 15N labeled proteins can be characterized by measuring the cross-correlation rates δN,NI that govern the conversion of Zeeman order Nz of an amide 15N nucleus into longitudinal two-spin order 2NzIz involving the amide 15N and 1H nuclei. This represents an alternative to the measurement of 15N self-relaxation rates 1/T1 and 1/T2 or 1/T1ρ. The rate of interconversion between Nz and 2NzIz is due to cross-correlation between fluctuations of different interactions and is not affected by a variety of relaxation mechanisms that contribute to the self-relaxation rates 1/T1, 1/T2 and 1/T1ρ. Spin diffusion among protons, which affects the measurements, can be quenched by various means that are evaluated by experiments and simulations. By applying an off-resonance radio-frequency (RF) field in the vicinity of the nitrogen resonance, the spectral density function J(ω) can be determined at the frequency origin and at the nitrogen Larmor frequency. The methods are applied to the paramagnetic High-Potential Iron-Sulfur Protein iso I (HiPIP I) from E. halophila in its reduced state.
    Type of Medium: Electronic Resource
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