Conformational studies on human and rabbit plasma hemopexin and on the effect of ligands on the rabbit heme-hemopexin complex

Mueller-Eberhard, Ursula; Grizzuti, Kaert

doi:10.1021/bi00787a015

Cited by 20 publications

(6 citation statements)

References 15 publications

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“…Cyanide affects both optical rotatory dispersion and circular dichroism of HPX-heme(III) (16). Furthermore, crystallographic analysis showed that cyanide binds to HPX-heme(III), detaching His213 from the heme (20).…”

Section: Cyanide Binding To Hpx-heme(iii)mentioning

confidence: 99%

“…1 CO causes a shift of the maximum of the optical absorption spectrum in the Soret band of HPX-heme(II) from 428 nm to 421 nm (i.e., HPX-heme(II)-CO) and a change of the extinction coefficient from e 428 nm ¼ 1.47610 5 M 71 cm 71 to e 421 nm ¼ 1.52610 5 M 71 cm 71 (17). Moreover, CO affects significantly both optical rotatory dispersion and circular dichroism of HPX-heme(II) (16).…”

Section: Co Binding To Hpx-heme(ii)mentioning

confidence: 99%

“…In particular, HPX-heme binds CO, . NO, and cyanide by detaching His213; however, O 2 induces HPX-heme(II) oxidation (16,17,19,20,24,25,27). Moreover, .…”

Section: Introductionmentioning

confidence: 99%

“…bands of HPX-heme(II)-CO are affected when CO is replaced by O 2 . Then, HPX-heme(II)-O 2 undergoes fast oxidation (16).…”

Section: Introductionmentioning

confidence: 99%

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Heme‐hemopexin: A ‘Chronosteric’ heme‐protein

Ascenzi

Fasano

2007

IUBMB Life

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SummaryHemopexin (HPX) serves as scavenger and transporter of toxic plasma heme to the liver. HPX is formed by two four-bladed b-propeller domains, resembling two thick disks that lock together at a 908 angle. The heme is bound between the two b-propeller domains in a pocket formed by the interdomain linker peptide. Residues His213 and His266 coordinate the heme iron atom giving a stable bis-histidyl complex. The HPX-heme geometry is reminiscent of heme-proteins endowed with ligand binding and (pseudo-) enzymatic properties. HPX-heme binds reversibly CO, NO/peroxynitrite scavenging. Heme sequestering by HPX prevents heme-mediated activation of oxidants which induce the lowdensity lipoprotein oxidation. Here, ligand binding and (pseudo-) enzymatic properties of HPX-heme are reviewed. HPX, acting not only as a heme carrier but also displaying transient heme-based ligand binding and (pseudo-)enzymatic properties, could be considered a 'chronosteric' heme-protein. IUBMB Life, 59: 700-708, 2007

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Section: Cyanide Binding To Hpx-heme(iii)mentioning

confidence: 99%

Section: Co Binding To Hpx-heme(ii)mentioning

confidence: 99%

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Heme‐hemopexin: A ‘Chronosteric’ heme‐protein

Ascenzi

Fasano

2007

IUBMB Life

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“…Ferrous heme-serum albumin has been reported to bind NO, O 2 and CO [14,[18][19][20][21], and to exhibit weak catalase and peroxidase activity [22]. HPXheme(II) binds CO and NO, however, O 2 induces HPX-heme(II) oxidation [17,[23][24][25][26][27]. Furthermore, HPX-heme(III) binds cyanide [16].…”

mentioning

confidence: 99%

Reductive nitrosylation and peroxynitrite‐mediated oxidation of heme–hemopexin

et al. 2006

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Hemopexin (HPX), which serves as a scavenger and transporter of toxic plasma heme, has been postulated to play a key role in the homeostasis of NO. In fact, HPX–heme(II) reversibly binds NO and facilitates NO scavenging by O2. HPX–heme is formed by two four‐bladed β‐propeller domains. The heme is bound between the two β‐propeller domains, residues His213 and His266 coordinate the heme iron atom. HPX–heme displays structural features of heme‐proteins endowed with (pseudo‐)enzymatic activities. In this study, the kinetics of rabbit HPX–heme(III) reductive nitrosylation and peroxynitrite‐mediated oxidation of HPX–heme(II)–NO are reported. In the presence of excess NO, HPX–heme(III) is converted to HPX–heme(II)–NO by reductive nitrosylation. The second‐order rate constant for HPX–heme(III) reductive nitrosylation is (1.3 ± 0.1) × 101 m−1·s−1, at pH 7.0 and 10.0 °C. NO binding to HPX–heme(III) is rate limiting. In the absence and presence of CO2 (1.2 × 10−3 m), excess peroxynitrite reacts with HPX–heme(II)–NO (2.6 × 10−6 m) leading to HPX–heme(III) and NO, via the transient HPX–heme(III)–NO species. Values of the second‐order rate constant for HPX–heme(III)–NO formation are (8.6 ± 0.8) × 104 and (1.2 ± 0.2) × 106 m−1·s−1 in the absence and presence of CO2, respectively, at pH 7.0 and 10.0 °C. The CO2‐independent value of the first‐order rate constant for HPX–heme(III)–NO denitrosylation is (4.3 ± 0.4) × 10−1 s−1, at pH 7.0 and 10.0 °C. HPX–heme(III)–NO denitrosylation is rate limiting. HPX–heme(II)–NO appears to act as an efficient scavenger of peroxynitrite and of strong oxidants and nitrating species following the reaction of peroxynitrite with CO2 (e.g. ONOOC(O)O–, CO3–, and NO2).

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