Binuclear Iron Site Research Articles

Allosteric interactions in sipunculid and brachiopod hemerythrins.

Chemical and spectroscopic consequences of allosteric interactions for ligand binding to sipunculid (Phascolopsis gouldii) and brachiopod (Lingula reevii) hemerythrins (Hrs) have been investigated. Possible allosteric effectors for homotropic effects in sipunculid Hrs have been examined, but only reduction in ligand affinity is observed without cooperativity. In contrast to sipunculid Hr, L. reevii Hr binds O2 cooperatively in the pH range 7-8 and exhibits a Bohr effect. Spectroscopic comparisons of the sipunculid and brachiopod Hrs show no significant differences in the active site structures; therefore, modulation of oxygen affinity is attributable to effects linking the site to quaternary structural changes in the octamer. Oxygen equilibria can be fit with a conformational model incorporating a minimum of three states, tensed (T), relaxed (R), and an R-T hybrid. Resonance Raman spectra of L. reevii oxyHr show a shift in the peroxo stretching frequency when the pH is lowered from pH 7.7 (predominantly R oxyHr) to pH 6.3 (a mixture of R, T, and R-T hybrid), but P. gouldii Hr does not have a frequency shift under the same conditions. In contrast to hemoglobins, ligand binding to the deoxy and met forms is noncooperative for brachiopod (and sipunculid) Hrs. It is thus suggested that conformational changes in the protein are linked to the oxidation state change that accompanies oxygenation of the coupled binuclear iron site (deoxy [FeIIFeII]----oxy [FeIIIFeIII]). The total allosteric energy expended in oxygenation is about 1.4 kcal/mol, and such a shift is possible in the relaxed-tense conversion with relatively limited constraints of the iron coordination environment via the protein quaternary structure. The mechanism of cooperativity in the binuclear copper oxygen carrier hemocyanin is discussed in light of these results.

Redox chemistry of sulfide-bridged derivatives of the binuclear iron site in hemerythrin from Phascolopsis gouldii

Redox chemistry of sulfide-bridged derivatives of the binuclear iron site in hemerythrin from Phascolopsis gouldii

ChemInform Abstract: CRYSTAL AND MOLECULAR STRUCTURE OF THE (μ‐OXO)BIS(AQUOBIS(PHENANTHROLINE)IRON(III)) COMPLEX, A RAMAN SPECTROSCOPIC MODEL FOR THE BINUCLEAR IRON SITE IN HEMERYTHRIN AND RIBONUCLEOTIDE REDUCTASE

Chemischer InformationsdienstVolume 16, Issue 7 Physical Organic Chemistry ChemInform Abstract: CRYSTAL AND MOLECULAR STRUCTURE OF THE (μ-OXO)BIS(AQUOBIS(PHENANTHROLINE)IRON(III)) COMPLEX, A RAMAN SPECTROSCOPIC MODEL FOR THE BINUCLEAR IRON SITE IN HEMERYTHRIN AND RIBONUCLEOTIDE REDUCTASE J. E. PLOWMAN, J. E. PLOWMANSearch for more papers by this authorT. M. LOEHR, T. M. LOEHRSearch for more papers by this authorC. K. SCHAUER, C. K. SCHAUERSearch for more papers by this authorO. P. ANDERSON, O. P. ANDERSONSearch for more papers by this author J. E. PLOWMAN, J. E. PLOWMANSearch for more papers by this authorT. M. LOEHR, T. M. LOEHRSearch for more papers by this authorC. K. SCHAUER, C. K. SCHAUERSearch for more papers by this authorO. P. ANDERSON, O. P. ANDERSONSearch for more papers by this author First published: February 19, 1985 https://doi.org/10.1002/chin.198507054AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume16, Issue7February 19, 1985 RelatedInformation