On the role of conserved proline residues in the structure and function of Clostridium pasteurianum 2[4Fe-4S] ferredoxin.
The widespread occurrence of Pro residues adjacent to Cys ligands in the sequences of [4Fe-4S] electron transfer proteins has not yet found a functional basis. The two such Pro of Clostridium pasteurianum 2[4Fe-4S] ferredoxin have been probed by site-directed mutagenesis. Any one of them, but not both simultaneously, can be substituted without impairing the proper folding of the protein. The reduction potentials of the ferredoxin variants fall in a narrow range of < 20 mV above the potential of the native protein. The biological activities with C. pasteurianum hydrogenase and pyruvate-ferredoxin oxidoreductase do not change significantly, except when Lys replaces Pro. In these cases, the data suggest that the two clusters of 2[4Fe-4S] ferredoxin may not always be equivalent in the interaction with the redox partners. Destabilization of the structure has been observed as the consequence of the Pro19 or Pro48 substitutions. Using 2-D NMR, this effect has been associated with perturbations of both the hydrogen bond network and one amino acid side chain around the [4Fe-4S] clusters. Thus, the conserved Pro found in the binding motif of [4Fe-4S] clusters in proteins strongly stabilizes the active site but does not play an essential role in the mechanism of electron transfer.
Quinkal
I
I
Département de Biologie Moléculaire et Structurale, CEN-Grenoble, France.
Davasse
V
V
Gaillard
J
J
Moulis
J M
JM
D000595:Amino Acid Sequence; D003013:Clostridium / Q000737:chemistry*; D004355:Drug Stability; D004579:Electron Transport; D005288:Ferredoxins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D006358:Hot Temperature; D006860:Hydrogen Bonding; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010084:Oxidation-Reduction; D011392:Proline; D016415:Sequence Alignment; D013329:Structure-Activity Relationship
D005288:Ferredoxins; D011392:Proline