title: Role of aromatic residues in stabilization of the [Fe4S4] cluster in high-potential iron proteins (HiPIPs): physical characterization and stability studies of Tyr-19 mutants of Chromatium vinosum HiPIP.
abstract: The functional role of residue Tyr-19 of Chromatium vinosum HiPIP has been evaluated by site-directed mutagenesis experiments. The stability of the [Fe4S4] cluster prosthetic center is sensitive to side-chain replacements. Polar residues result in significant instability, while nonpolar residues (especially with aromatic side chains) maintain cluster stability. Two-dimensional NMR data of native and mutant HiPIPs are consistent with a model where Tyr-19 serves to preserve the structural rigidity of the polypeptide backbone, thereby maintaining a hydrophobic barrier for exclusion of water from the cluster cavity. Solvent accessibility results in more facile oxidation of the cluster by atmospheric oxygen, with subsequent rapid hydrolysis of the [Fe4S4]3+ core.
authors.affiliation: Evans Laboratory of Chemistry, Ohio State University, Columbus 43210, USA.
authors.forename: A
authors.initials: A
authors.lastname: Agarwal
authors.forename: D
authors.initials: D
authors.lastname: Li
authors.forename: J A
authors.initials: JA
authors.lastname: Cowan
mesh_terms: D000332:Aerobiosis; D000693:Anaerobiosis; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics; D002844:Chromatium / Q000737:chemistry*; D007501:Iron / Q000737:chemistry*; D007506:Iron-Sulfur Proteins / Q000737:chemistry* / Q000235:genetics; D009682:Magnetic Resonance Spectroscopy; D016297:Mutagenesis, Site-Directed; D010084:Oxidation-Reduction; D045322:Photosynthetic Reaction Center Complex Proteins; D011199:Potentiometry; D013455:Sulfur / Q000737:chemistry*; D014443:Tyrosine / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D007506:Iron-Sulfur Proteins; D045322:Photosynthetic Reaction Center Complex Proteins; C007943:high potential iron-sulfur protein; D014443:Tyrosine; D013455:Sulfur; D007501:Iron