Modeling the hydrogen sulfide binding to heme

• Published in: Journal of inorganic biochemistry 2018-07, Vol.184, p.108-114
• Main Authors: Ostojić, B.D., Schwerdtfeger, P., Đorđević, D.S.
• Format: Article
• Language: English
• Subjects: Coupled cluster theory; Density functional theory; Electronic states; H2S binding; Heme; Imidazole
• ISSN: 0162-0134; 1873-3344
• DOI: 10.1016/j.jinorgbio.2018.04.012

The binding of hydrogen sulfide to a model heme compound is investigated by coupled-cluster singles-doubles augmented by a perturbative triple excitations, CCSD(T), and density functional theory, DFT. The minimum energy path for the H2S addition to an isolated heme center of the heme protein is evaluated by adopting as a model the heme compound FeP(Im) (P = porphyrin; Im = imidazole). The FeP(Im)-H2S aduct is bound by 13.7 kcal/mol at the CCSD(T) level of theory. Relaxed potential energy curves for the lowest lying spin states of the H2S to FeP(Im) binding using DFT reveal that the binding process is associated with a “double spin-crossover” reaction with the existence of long-distance van der Waals minima only 5–7 kcal/mol above the FeP(Im)-H2S ground state. The fact that the energy of the singlet ground state of FeP(Im)-H2S is so close in energy to the dissociation products FeP(Im) + H2S points towards the reversibility of the H2S adsorption/desorption process in biochemical reactions. [Display omitted] •The H2S binding to a heme model molecule is investigated by quantum theoretical methods.•The binding energy for the H2S-FeP(imidazole) complex is estimated to be 13.7 kcal/mol.•Density functional theory (DFT) and coupled cluster calculations (CCSD(T)) are employed.•Results point towards the reversibility of the H2S adsorption/desorption process.