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  • 1
    Electronic Resource
    Electronic Resource
    Characterisation of oxidised 7Fe dicluster ferredoxins with NMR spectroscopy (2000)
    Springer
    JBIC 5 (2000), S. 432-447 
    Details
    ISSN: 1432-1327
    Keywords: Key words NMR spectroscopy ; Ferredoxins ; Dicluster ; Hyperfine shifts ; Cluster ligands
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Dicluster ferredoxins (Fds) from Sulfolobus acidocaldarius and Desulfovibrio africanus (FdIII) have been studied using 1H NMR. Both wild-type proteins contain a [3Fe-4S]+/0 and a [4Fe-4S]2+/+ cluster as isolated. The [4Fe-4S]2+/+ cluster (cluster II) is bound by cysteine residues arranged in a classic ferredoxin motif: CysI-(Xaa)2-CysII-(Xaa)2-CysIII-(Xaa) n -CysIV-Pro, whilst the binding motif of the [3Fe-4S]+/0 cluster (cluster I) has a non-ligating aspartic acid (Asp14) at position II, i.e. CysI-(Xaa)2-Asp-(Xaa)2-CysIII. D. africanus FdIII undergoes facile cluster transformation from the 7Fe form to the 8Fe form, but S. acidocaldarius Fd does not. Many factors determine the propensity of a cluster to undergo interconversion, including the presence, and correct orientation, of a suitable ligand. We have investigated this using 1H NMR by introducing a potential fourth ligand into the binding motif of cluster I of D. africanus FdIII. Asp14 has been mutated to cysteine (D14C), glutamic acid (D14E) and histidine (D14H). Cluster incorporation was performed in vitro. The cluster types present were identified from the chemical shift patterns and temperature-dependent behaviour of the hyperfine-shifted resonances. Factors influencing cluster ligation and cluster interconversion, in vitro, are discussed. Furthermore, the data have established that the residue at position II in the cluster binding motif of cluster I is influential in determining the chemical shift pattern observed for a [3Fe-4S]+ cluster when a short/symmetric binding motif is present. Based on this, a series of rules for characterising the 1H NMR chemical shifts of mono- and di-cluster [3Fe-4S]+ cluster-containing ferredoxins is given.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s007750050003
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  • 2
    Electronic Resource
    Electronic Resource
    Effect of nickel(II) substitution on the resonance Raman and NMR spectra of Alcaligenes xylosoxidans azurin II: implications for axial-ligand bonding interactions in cupredoxin active sites (1998)
    Springer
    JBIC 3 (1998), S. 282-291 
    Details
    ISSN: 1432-1327
    Keywords: Key words Resonance Raman spectroscopy ; Azurin ; Cupredoxins ; Axial ligands ; NMR spectroscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract  Assignment of the resonance Raman (RR) spectrum of Ni(II)-substituted azurin II from Alcaligenes xylosoxidans (NCIMB 11015) using Ni isotope substitution reveals an anomalously low Ni-S(Cys) stretching frequency of 349 cm–1, suggesting the presence of significant axial-ligand bonding interactions. The X-ray crystal structure of Ni(II)-substituted azurin from Pseudomonas aeruginosa shows that there are two potential axial ligands to the Ni ion: a peptide carbonyl O at a distance of 2.46 Å, together with a long-range interaction from a methionine sulfur (S′) at a distance of 3.30 Å. Comparison of the RR properties of Ni(II)-substituted azurin II with stellacyanin (which contains an axial carbonyl ligand, but no methionine) suggests that the interaction from the carbonyl oxygen ligand alone is not sufficient to account for the weak Ni azurin metal-thiolate bond. Instead, it appears that a Ni-methionine bonding interaction is also required to explain the low Ni-S(Cys) stretching frequency in Ni(II)-substituted azurin II. This hypothesis is supported by NMR studies which show a large paramagnetic shift for the protons of the methionine side-chain. Thus, it appears that Ni-substituted azurin II is best described as five-coordinate, and that significant Ni(II)-methionine bonding interactions can occur at a distance of 3.3 Å.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s007750050233
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    Paper (German National Licenses)
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