Ma-Pgb* fold.

<p>(Panel A) The secondary structure elements are labeled A–H’. The 20 <i>N</i>-terminal residues and the extended CE and FG loops that seal the heme pocket and prevent the access of small ligands to the heme distal cavity are in orange. The pre-A Z-helix is in green. The heme (red) is displayed edge on. The proximal HisF8 residue is shown on the left hand side of the heme. The picture includes the mutated SerE20 residue, located at the <i>C</i>-terminus of the E-helix. The HisF8 and SerE20 side chains and residues building up the heme distal pocket are drawn as skeletal models (C atoms yellow, N atoms blue, and O atoms red) and labeled. (Panel B) Mono views of “tunnel 1” (top) and “tunnel 2” (bottom) access sites in Ma-Pgb*. Helices flanking the tunnel entries are labelled. The heme group (seen through the tunnel apertures) is shown in red. The protein is correctly oriented in both images, to bring each tunnel in the direction of sight. The images are rotated by 90°. The pictures have been drawn by UCSF - Chimera <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0095391#pone.0095391-Pettersen1" target="_blank">[55]</a>. For details, see ref. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0095391#pone.0095391-Nardini1" target="_blank">[11]</a>.</p

Dependence of <i>h</i> on the Ma-Pgb*-Fe(III) and Ma-Pgb*-Fe(III)-azide concentration (open and filled triangles, respectively) for the peroxynitrite isomerization, at pH 7.4 and 20°C.

<p>The continuous line was calculated according to Eq. 5 with <i>h</i>_app = 3.8×10⁴ M^–1 s⁻¹ and <i>k</i>₀ = 2.8×10^–1 s⁻¹. The average value of <i>h</i>₀ obtained in the presence of Ma-Pgb*-Fe(III)-azide (filled triangles) is 2.7×10^–1 s⁻¹. The peroxynitrite concentration was 2.5×10^–4 M. The azide concentration was 1.0×10^–1 M. Where not shown, the standard deviation is smaller than the symbol. For details, see text.</p

Values of the second-order rate constant for the nitrite-reductase activity of ferrous heme-proteins.

a<p>pH 7.0; unknown temperature <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0095391#pone.0095391-Sturms1" target="_blank">[42]</a>.</p>b<p>pH 7.4 and 25°C. From <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0095391#pone.0095391-Tiso2" target="_blank">[45]</a>.</p>c<p>CysE20Ser mutant. pH 7.4 and 20°C. Present study.</p>d<p>pH 7.6 and 25°C. From <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0095391#pone.0095391-Helbo1" target="_blank">[49]</a>.</p>e<p>pH 7.4 and 25°C. From <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0095391#pone.0095391-Tiso1" target="_blank">[43]</a>.</p>f<p>pH 7.4 and 25°C. From <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0095391#pone.0095391-Huang1" target="_blank">[37]</a>.</p>g<p>pH 7.4 and 25°C. From <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0095391#pone.0095391-Tiso1" target="_blank">[43]</a>.</p>h<p>pH 7.4 and 25°C. From <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0095391#pone.0095391-Petersen1" target="_blank">[40]</a>.</p>i<p>pH 7.0 and 25°C. From <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0095391#pone.0095391-Li1" target="_blank">[44]</a>.</p>j<p>pH 7.4 and 25°C. From <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0095391#pone.0095391-Tiso1" target="_blank">[43]</a>. In “Human neuroglobin CysCD4-CysD5”, the CysCD4 and CysD5 residues form an intramolecular disulphide bond.</p>k<p>pH 7.4 and 25°C. From <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0095391#pone.0095391-Tiso1" target="_blank">[43]</a>. In “Human neuroglobin CysCD4/CysD5”, the CysCD4 and CysD5 residues do not form the intramolecular disulphide bond.</p>l<p>pH 7.4 and 25°C. From <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0095391#pone.0095391-Tiso1" target="_blank">[43]</a>.</p>m<p>pH 7.4 and 20°C. From <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0095391#pone.0095391-Ascenzi8" target="_blank">[46]</a>.</p>n<p>pH 7.4 and 25°C. From <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0095391#pone.0095391-Li1" target="_blank">[44]</a>.</p

Values of the second-order rate constant for peroxynitrite isomerization by ferric heme-proteins.

a<p>pH 7.4 and 20°C. Present study.</p>b<p>pH 7.0 and 20°C. From <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0095391#pone.0095391-Ascenzi7" target="_blank">[32]</a>.</p>c<p>pH 7.0 and 20°C. From <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0095391#pone.0095391-Coppola1" target="_blank">[31]</a>.</p>d<p>pH 7.0 and 20°C. From <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0095391#pone.0095391-Herold2" target="_blank">[22]</a>.</p>e<p>pH 7.5 and 20°C. From <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0095391#pone.0095391-Herold4" target="_blank">[24]</a>.</p>f<p>pH 7.5 and 20°C. From <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0095391#pone.0095391-Herold2" target="_blank">[22]</a>.</p>g<p>pH 7.2 and 22°C. From <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0095391#pone.0095391-Ascenzi4" target="_blank">[28]</a>.</p>h<p>pH 7.0 and 20°C. Cardiolipin was 1.6×10^–4 M. From <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0095391#pone.0095391-Ascenzi5" target="_blank">[29]</a>.</p

Difference absorbance spectra of Ma-Pgb*-Fe(II) <i>minus</i> Ma-Pgb*-Fe(II)-NO, at pH 7.4 and 20°C.

<p>The overall difference spectrum, the difference spectrum of the fast phase, and the difference spectrum of the slow phase are represented by diamonds, squares, and circles, respectively. For details, see text.</p

Normalized averaged time courses of the NO₂^–-mediated nitrosylation of Ma-Pgb*-Fe(II), in the absence and presence of CO, at pH 7.4 and 20°C, λ = 430 nm.

<p>The NO₂^– concentration was 2.5×10^–3 M (traces a and b) and 8.0×10^–3 M (trace c). The CO concentration was 1.0×10^–4 M (trace a). CO inhibits the NO₂^–-mediated nitrosylation of Ma-Pgb*-Fe(II) (trace a). The time course analysis according to Eqn. 1 allowed the determination of the following parameters: trace b, α₁ = 0.58±0.05, <i>k</i>_obs1 = (2.3±0.2) ×10^–2 s^–1, α₂ = 0.42±0.04, and <i>k</i>_obs2 = (3.2±0.3)×10^–3 s^–1; trace c, α₁ = 0.56±0.05, <i>k</i>_obs1 = (7.9±0.8)×10^–2 s^–1, α₂ = 0.44±0.04, and <i>k</i>_obs2 = (9.0±0.1)×10^–3 s^–1. For details, see text.</p

Values of kinetic parameters for Ma-Pgb*-Fe reactivity.

a<p>pH 7.0 and 20°C. From <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0095391#pone.0095391-Abbruzzetti1" target="_blank">[15]</a>.</p>b<p>pH 7.2 and 22°C. From <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0095391#pone.0095391-Ascenzi1" target="_blank">[16]</a>.</p>c<p>pH 7.4 and 20°C. Present study.</p>d<p>pH 7.0 and 20°C. From <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0095391#pone.0095391-Ciaccio1" target="_blank">[18]</a>.</p>e<p>pH 9.2 and 20°C. From <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0095391#pone.0095391-Pesce4" target="_blank">[17]</a>.</p

pH dependence of Log <i>k</i>_app1 (M^–1 s^–1; squares) and Log <i>k</i>_app2 (M^–1 s^–1; circles) for the Ma-Pgb*-Fe(II) reductase activity.

<p>The slope of the continuous lines is: –1.01±0.03 (squares) and –1.05±0.02 (circles). The standard deviation is smaller than the symbol. For details, see text.</p

Values of <i>K</i>_I for the competitive inhibition of the HSA-Tyr411-catalyzed hydrolysis of NphOAc, NphOHe, NphODe, and NphOMy by diazepam, diflunisal, ibuprofen, 3-indoxyl-sulfate, and/or propofol, at pH 7.5 and 22.0°C.

<p>^a From [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0120603#pone.0120603.ref013" target="_blank">13</a>]. ^b Present study. ^c From [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0120603#pone.0120603.ref012" target="_blank">12</a>].</p

Values of the second-order rate constant for peroxynitrite isomerization by ferric heme-proteins.

a<p>pH 7.4 and 20°C. Present study.</p>b<p>pH 7.0 and 20°C. From <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0095391#pone.0095391-Ascenzi7" target="_blank">[32]</a>.</p>c<p>pH 7.0 and 20°C. From <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0095391#pone.0095391-Coppola1" target="_blank">[31]</a>.</p>d<p>pH 7.0 and 20°C. From <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0095391#pone.0095391-Herold2" target="_blank">[22]</a>.</p>e<p>pH 7.5 and 20°C. From <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0095391#pone.0095391-Herold4" target="_blank">[24]</a>.</p>f<p>pH 7.5 and 20°C. From <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0095391#pone.0095391-Herold2" target="_blank">[22]</a>.</p>g<p>pH 7.2 and 22°C. From <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0095391#pone.0095391-Ascenzi4" target="_blank">[28]</a>.</p>h<p>pH 7.0 and 20°C. Cardiolipin was 1.6×10^–4 M. From <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0095391#pone.0095391-Ascenzi5" target="_blank">[29]</a>.</p