2bcn
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(New page: 200px<br /><applet load="2bcn" size="450" color="white" frame="true" align="right" spinBox="true" caption="2bcn, resolution 1.700Å" /> '''Solvent isotope eff...)
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Revision as of 06:36, 21 November 2007
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Solvent isotope effects on interfacial protein electron transfer between cytochrome c and cytochrome c peroxidase
Overview
D(2)O-grown crystals of yeast zinc porphyrin substituted cytochrome c, peroxidase (ZnCcP) in complex with yeast iso-1-cytochrome c (yCc) diffract, to higher resolution (1.7 A) and pack differently than H(2)O-grown, crystals (2.4-3.0 A). Two ZnCcP's bind the same yCc, (porphyrin-to-porphyrin separations of 19 and 29 A), with one ZnCcP, interacting through the same interface found in the H(2)O crystals. The, triplet excited-state of at least one of the two unique ZnCcP's is, quenched by electron transfer (ET) to Fe(III)yCc (k(e) = 220 s(-1))., Measurement of thermal recombination ET between Fe(II)yCc and ZnCcP+ in, the D(2)O-treated crystals has both slow and fast components that differ, by 2 orders of magnitude (k(eb)(1) = 2200 s(-1), k(eb)(2) = 30 s(-1))., Back ET in H(2)O-grown crystals is too fast for observation, but soaking, H(2)O-grown crystals in D(2)O for hours generates slower back ET, with, kinetics similar to those of the D(2)O-grown crystals (k(eb)(1) = 7000, s(-1), k(eb)(2) = 100 s(-1)). Protein-film voltammetry of yCc adsorbed to, mixed alkanethiol monolayers on gold electrodes shows slower ET for, D(2)O-grown yCc films than for H(2)O-grown films (k(H) = 800 s(-1); k(D) =, 540 s(-1) at 20 degrees C). Soaking H(2)O- or D(2)O-grown films in the, counter solvent produces an immediate inverse isotope effect that, diminishes over hours until the ET rate reaches that found in the counter, solvent. Thus, D(2)O substitution perturbs interactions and ET between yCc, and either CcP or electrode films. The effects derive from slow exchanging, protons or solvent molecules that in the crystal produce only small, structural changes.
About this Structure
2BCN is a Protein complex structure of sequences from Saccharomyces cerevisiae with ZNH and HEM as ligands. Active as Cytochrome-c peroxidase, with EC number 1.11.1.5 Full crystallographic information is available from OCA.
Reference
Solvent isotope effects on interfacial protein electron transfer in crystals and electrode films., Kang SA, Hoke KR, Crane BR, J Am Chem Soc. 2006 Feb 22;128(7):2346-55. PMID:16478190
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