1b9r
TERPREDOXIN FROM PSEUDOMONAS SP.
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OverviewOverview
Terpredoxin (Tdx) is a 105-residue bacterial ferredoxin consisting of a, single polypeptide chain and a single Fe2S2 prosthetic group. Tdx was, first identified in a strain of Pseudomonas sp. capable of using, alpha-terpineol as sole carbon source. The Tdx gene, previously cloned, from the plasmid-encoded terp operon, that carries genes encoding for, proteins involved in terpineol catabolism, has been subcloned and, expressed as the holoprotein in E. coli. Physical characterization of the, expressed Tdx has been performed, and a model for the solution structure, of oxidized Tdx (Tdxo) has been determined. High-resolution homo- and, heteronuclear NMR data have been used for structure determination in, diamagnetic regions of the protein. The structure of the metal binding, site (which cannot be determined directly by NMR methods due to, paramagnetic broadening of resonances) was modeled using restraints, obtained from a crystal structure of the homologous ferredoxin adrenodoxin, (Adx) and loose restraints determined from paramagnetic broadening, patterns in NMR spectra. Essentially complete 1H and 15N NMR resonance, assignments have been made for the diamagnetic region of Tdxo (ca. 80% of, the protein). A large five-stranded beta-sheet and a smaller two-stranded, beta-sheet were identified, along with three alpha-helices. A high degree, of structural homology was observed between Tdx and two other ferredoxins, with sequence and functional homology to Tdx for which structures have, been determined, Adx and putidaredoxin (Pdx), a homologous Pseudomonas, protein. 1H/2H exchange rates for Tdx backbone NH groups were measured for, both oxidation states and are rationalized in the context of the Tdx, structure. In particular, an argument is made for the importance of the, residue following the third ligand of the metal cluster (Arg49 in Tdx, His49 in Pdx, His56 in Adx) in modulating protein dynamics as a function, of oxidation state. Some differences between Tdx and Pdx are detected by, UV-visible spectroscopy, and structural differences at the C-terminal, region were also observed. Tdx exhibits only 2% of the activity of Pdx in, turnover assays performed using the reconstituted camphor hydroxylase, system of which Pdx is the natural component.
About this StructureAbout this Structure
1B9R is a Single protein structure of sequence from Pseudomonas sp. with FES as ligand. Full crystallographic information is available from OCA.
ReferenceReference
A model for the solution structure of oxidized terpredoxin, a Fe2S2 ferredoxin from Pseudomonas., Mo H, Pochapsky SS, Pochapsky TC, Biochemistry. 1999 Apr 27;38(17):5666-75. PMID:10220356
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