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PDBsum entry 1e10
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Iron-sulfur protein
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PDB id
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1e10
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Contents |
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* Residue conservation analysis
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References listed in PDB file
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Key reference
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Title
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A two-Alpha-Helix extra domain mediates the halophilic character of a plant-Type ferredoxin from halophilic archaea.
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Authors
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B.L.Marg,
K.Schweimer,
H.Sticht,
D.Oesterhelt.
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Ref.
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Biochemistry, 2005,
44,
29-39.
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PubMed id
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Abstract
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The [2Fe-2S] ferredoxin (HsFdx) of the halophilic archaeon Halobacterium
salinarum exhibits a high degree of sequence conservation with plant-type
ferredoxins except for an insertion of 30 amino acids near its N-terminus which
is extremely rich in acidic amino acids. Unfolding studies reveal that HsFdx has
an unfolding temperature of approximately 85 degrees C in 4.3 M NaCl, but of
only 50 degrees C in low salinity, revealing its halophilic character. The
three-dimensional structure of HsFdx was determined by NMR spectroscopy,
resulting in a backbone rmsd of 0.6 A for the diamagnetic regions of the
protein. Whereas the overall structure of HsFdx is very similar to that of the
plant-type ferredoxins, two additional alpha-helices are found in the acidic
extra domain. (15)N NMR relaxation studies indicate that HsFdx is rigid, and the
flexibility of residues is similar throughout the molecule. Monitoring protein
denaturation by NMR did not reveal differences between the core fold and the
acidic domain, suggesting a cooperative unfolding of both parts of the molecule.
A mutant of the HsFdx in which the acidic domain is replaced with a short loop
of the nonhalophilic Anabaena ferredoxin shows a considerably changed expression
pattern. The halophilic wild-type protein is readily expressed in large amounts
in H. salinarum, but not in Escherichia coli, whereas the mutant ferredoxin
could only be overexpressed in E. coli. The salt concentration was also found to
play a critical role for the efficiency of cluster reconstitution: the cluster
of HsFdx could be reconstituted only in a solution containing molar
concentrations of NaCl, while the reconstitution of the cluster in the mutant
protein proceeds efficiently in low salt. These findings suggest that the acidic
domain mediates the halophilic character which is reflected in its
thermostability, the exclusive expression in H. salinarum, and the ability to
efficiently reconstitute the iron-sulfur cluster only at high salt
concentrations.
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Secondary reference #1
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Title
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Sequence-Specific 1h, 13c and 15n resonance assignments and secondary structure of [2fe-2s] ferredoxin from halobacterium salinarum.
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Authors
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K.Schweimer,
B.L.Marg,
D.Oesterhelt,
P.Rösch,
H.Sticht.
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Ref.
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J Biomol Nmr, 2000,
16,
347-348.
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PubMed id
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