INVESTIGADORES
ESTRIN Dario Ariel
artículos
Título:
Reactivity of Inorganic Sulfide Species toward a Heme Protein Model
Autor/es:
S.A. BIEZA; F. BOUBETA; A. FEIS; G. SMULEVICH; D.A. ESTRIN; L. BOECHI; S.E. BARI
Revista:
INORGANIC CHEMISTRY
Editorial:
AMER CHEMICAL SOC
Referencias:
Lugar: Washington; Año: 2015 vol. 54 p. 527 - 533
ISSN:
0020-1669
Resumen:
The reactivity of inorganic sulfide species toward heme peptides was
explored under biorelevant conditions in order to unravel the molecular
details of the reactivity of the endogenous hydrogen sulfide toward heme
proteins. Unlike ferric porphyrinates, which are reduced by inorganic
sulfide, some heme proteins can form stable FeIII?sulfide
adducts. To isolate the protein factors ruling the redox chemistry, we
used as a system model, the undecapeptide microperoxidase (MP11), a heme
peptide derived from cytochrome c proteolysis that retains the proximal
histidine bound to the FeIII atom. Upon addition of gaseous hydrogen sulfide (H2S)
at pH 6.8, the UV?vis spectra of MP11 closely resembled those of the
low-spin ferric hydroxo complex (only attained at an alkaline pH) and
cysteine or alkylthiol derivatives, suggesting that the FeIII reduction was prevented. The low-frequency region of the resonance Raman spectrum revealed the presence of an FeIII?S band at 366 cm?1 and the general features of a low-spin hexacoordinated heme. Anhydrous sodium sulfide (Na2S)
was the source of sulfide of choice for the kinetic evaluation of the
process. Theoretical calculations showed no distal stabilization
mechanisms for bound sulfide species in MP11, highlighting a key role of
the proximal histidine for the stabilization of the FeIII?S
adducts of heme compounds devoid of distal counterparts, which is
significant with regard to the biochemical reactivity of endogenous
hydrogen sulfide.