Circular Dichroism Studies of Hemoproteins and Heme Models

Myer, Yash P.; Pande, Ajay

doi:10.1016/b978-0-12-220103-5.50013-1

Cited by 56 publications

(53 citation statements)

References 115 publications

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“…Heme spectroscopic properties allow the investigation of functional and structural aspects of heme-bound proteins by optical absorption spectroscopy, CD, and 1 H-NMR relaxometry [4,35,36,[45][46][47]. Relaxivity in heme-proteins is usually due to second-sphere contributions, i.e., water molecules bound to the protein in the close proximity of a paramagnetic metal center and able to exchange with the bulk water [35][36][37].…”

Section: Discussionmentioning

confidence: 99%

Reversible two-step unfolding of heme–human serum albumin: a 1H-NMR relaxometric and circular dichroism study

Fanali¹,

Sanctis²,

Gioia³

et al. 2008

J Biol Inorg Chem

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Human serum albumin (HSA) participates in heme scavenging, the bound heme turning out to be a reactivity center and a powerful spectroscopic probe. Here, the reversible unfolding of heme-HSA has been investigated by 1 H-NMR relaxometry, circular dichroism, and absorption spectroscopy. In the presence of 6 equiv of myristate (thus fully saturating all available fatty acid binding sites in serum heme-albumin), 1.0 M guanidinium chloride induces some unfolding of heme-HSA, leading to the formation of a folding intermediate; this species is characterized by increased relaxivity and enhanced dichroism signal in the Soret region, suggesting a more compact heme pocket conformation. Heme binds to the folding intermediate with

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Section: Discussionmentioning

confidence: 99%

Reversible two-step unfolding of heme–human serum albumin: a 1H-NMR relaxometric and circular dichroism study

Fanali¹,

Sanctis²,

Gioia³

et al. 2008

J Biol Inorg Chem

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“…Several environmental factors have been shown to influence the sign of Soret CD spectra of heme proteins. Thus, the mirror image Soret CD spectra of AOS and BLC can likely be attributed to differences in the size or hydrophobicity of their active site heme environments (42,43). The Soret CD sign difference could also be explained as a result of flipping of the heme by 180°about an in-plane axis (44).…”

Section: Discussionmentioning

confidence: 99%

Characterization of the Coral Allene Oxide Synthase Active Site with UV−Visible Absorption, Magnetic Circular Dichroism, and Electron Paramagnetic Resonance Spectroscopy: Evidence for Tyrosinate Ligation to the Ferric Enzyme Heme Iron

et al. 2001

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Coral allene oxide synthase (AOS), a hemoprotein with weak sequence homology to catalase, is the N-terminal domain of a naturally occurring fusion protein with an 8R-lipoxygenase. AOS converts 8R-hydroperoxyeicosatetraenoic acid to the corresponding allene oxide. The UV-visible absorption and magnetic circular dichroism spectra of ferric AOS and of its cyanide and azide complexes, and the electron paramagnetic resonance spectra of native AOS (high-spin, g ) 6.56, 5.22, 2.00) and of its cyanide adduct (low-spin, g ) 2.86, 2.24, 1.60) closely resemble the corresponding spectra of bovine liver catalase (BLC). These results provide strong evidence for tyrosinate ligation to the heme iron of AOS as has been established for catalases. On the other hand, the positive circular dichroism bands in the Soret region for all three derivatives of ferric AOS are almost the mirror image of those in catalase. In addition, the cyanide affinity of native AOS (K d ) 10 mM at pH 7) is about 3 orders of magnitude lower than that of BLC. Thus, while these results conclusively support a common tyrosinate-ligated heme in AOS as in catalase, significant differences exist in the interaction between their respective heme prosthetic groups and protein environments, and in the access of small molecules to the heme iron.Interest in the enzymology underlying the high prostaglandin content of the Caribbean sea whip coral, Plexaura homomalla, has been the impetus for several biochemical investigations. Arachidonic acid is metabolized in extracts of P. homomalla and related corals by a lipoxygenase (LOX) 1 pathway that appeared initially to relate to the production of cyclopentenone prostaglandins (1, 2). An 8R-lipoxygenase converts arachidonic acid to 8R-hydroperoxyeicosatetraenoic acid (8R-HPETE), and the fatty acid hydroperoxide is then enzymatically dehydrated to an allene oxide, an epoxide with a propensity to cyclize to cyclopentenone derivatives. Brash et al., in 1997, isolated the cDNA of an 8R-lipoxygenase from P. homomalla and found it to occur with an extra sequence in the open reading frame that encodes the allene oxide synthase (AOS) (3). This natural fusion protein in coral consists of a LOX C-terminal domain (79 kDa) and an AOS N-terminal domain (43 kDa). The truncated (AOS) construct catalyzes an identical reaction to the AOS domain in the fusion protein, converting 8R-HPETE solely to the allene oxide. The truncated construct exhibits very high turnover number (1400/s) (4), although, due to the weaker expression of the fusion protein in E. coli, the comparable values for the fusion protein remain to be determined. 2 Although allene oxide has not proven to be an intermediate in the prostaglandin synthesis pathway (5), it may be linked to prostanoid type products such as clavulones and punaglandins of other corals (2,6,7). Allene oxides are very unstable epoxides; they readily hydrolyze into ketols, cyclopentenones, and other rearrangement products (8-10).The production of allene oxides from fatty acid hydroperoxides also ...

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“…7b). A two-signed CD behavior in the Soret region is frequently observed for Fe(II)-CO complexes of heme proteins [43][44][45] and only reflects the fact that the Soret band encompasses two nearly degenerate transitions [46]. In the present case, the opposite CD pattern displayed by the Fe(II)-CO complexes of heme-H and heme-GH is probably due to the fact that the isomer with dominant CD activity is different in the two cases.…”

Section: Spectroscopic Propertiesmentioning

confidence: 94%

pH-dependent redox and CO binding properties of chelated protoheme-l-histidine and protoheme-glycyl-l-histidine complexes

et al. 2005

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The pH dependence of redox properties, spectroscopic features and CO binding kinetics for the chelated protohemin-6(7)-L-histidine methyl ester (heme-H) and the chelated protohemin-6(7)-glycyl-L-histidine methyl ester (heme-GH) systems has been investigated between pH 2.0 and 12.0. The two heme systems appear to be modulated by four protonating groups, tentatively identified as coordinated H 2 O, one of heme's propionates, Ne of the coordinating imidazole, and the carboxylate of the histidine residue upon hydrolysis of the methyl ester group (in acid medium). The pK a values are different for the two hemes, thus reflecting structural differences. In particular, the different strain at the Fe-N e bond, related to the different length of the coordinating arm, results in a dramatic alteration of the bond strength, which is much smaller in heme-H than in heme-GH. It leads to a variation in the variation of the pKa for the protonation of the N e of the axial imidazole as well as in the proton-linked behavior of the other protonating groups, envisaging a cross-talk communication mechanism among different groups of the heme, which can be operative and relevant also in the presence of the protein matrix.

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Circular Dichroism Studies of Hemoproteins and Heme Models

Cited by 56 publications

References 115 publications

Reversible two-step unfolding of heme–human serum albumin: a 1H-NMR relaxometric and circular dichroism study

Reversible two-step unfolding of heme–human serum albumin: a 1H-NMR relaxometric and circular dichroism study

Characterization of the Coral Allene Oxide Synthase Active Site with UV−Visible Absorption, Magnetic Circular Dichroism, and Electron Paramagnetic Resonance Spectroscopy: Evidence for Tyrosinate Ligation to the Ferric Enzyme Heme Iron

pH-dependent redox and CO binding properties of chelated protoheme-l-histidine and protoheme-glycyl-l-histidine complexes

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