Cytochrome P-450 Model (Porphinato)(thiolato)iron(III) Complexes with Single and Double NH···S Hydrogen Bonds at the Thiolate Site

Abstract

Cytochrome P-450 contains a cysteine thiolate ligand at the axial position of (porphinato)iron(III) core. The axial thiolate has been shown to promote the heterolysis of the coordinated dioxygen upon sequential donation of electron and proton. 1-3 The crystallographic structure of cytochrome P-450 cam reported by Poulos et al. 4 has suggested the presence of weak double NH‚‚‚S hydrogen bonds between S of Cys 357 and two amide NHs of Gly 359 and Gln 360, as shown in Figure 1a. Recently, the presence of two clear NH‚‚‚S hydrogen bonds was reported for the crystal structure of chloroperoxidase. 5 Similar hydrogen bonds are found in the active site of P-450 BM-3 , 6 P-450 terp , 7 and P-450 eryF . 8 For P-450 cam , a molecular dynamics simulation from the reported crystallographic structure results in the shortening of the NH‚‚‚S hydrogen bond distances. 9 Furthermore, comparison of the Protein Data Bank crystallographical structural parameters at the active sites of substrate-bound P-450 cam with substrate-free P-450 cam 10 indicates shorter N‚‚‚S distance at the active site of the substrate-bound P-450 cam accompanied by a positive shift of the reported redox potential. 11 A remarkable effect on the electrochemical properties by NH‚‚‚S hydrogen bond have already been revealed by us for various metal thiolate complexes 12-14 as well as iron-sulfur proteins. [15][16][17] In order

Synthesis and molecular structures of S-2-FcNHCOC6H4SH and [MIII(OEP)(S-2-FcNHCOC6H4)] (Fc = ferrocenyl, M = Fe, Ga): Electrochemical contributions of intramolecular SH⋯O C and NH⋯S hydrogen bonds

“…On the other hand, intramolecular NHÁ Á ÁS hydrogen bond positively shifts the redox potential of various metal thiolates [7][8][9][10][11][12][13]. Especially, electron-withdrawing group, that is CF 3 , strengthens the hydrogen bond which results in a large positive shift [3,7].…”

Conformational Switching Between Acids and their Anions by Hydrogen Bonding

“…In contrast, the FeÀS bond distance in P450 model porphyrin complexes slightly elongates with NHÁ Á ÁS hydrogen bonding, as it does for the similar Ga(III) complex [55,56]. IR shifts for [Fe III (OEP)(S-tBuCONHC 6 H 4 )] (OEP ¼ octaethylphorphinato) and [Ga III (OEP)(S-t-BuCONHC 6 H 4 )] indicate the presence of a relatively weak NHÁ Á ÁS hydrogen bond.…”

Electronic features and hydrogen bonding capacity of the sulfur acceptor in thioureido-based compounds. Part 2. Further insight by theoretical charge density study

“…Although a number of studies indicate the significance of DAHÁ Á ÁS interactions for structure and function of biological systems [1][2][3][4][5][6][7][8][9][10][11] as well as inorganic materials [12][13][14][15][16] the acceptor abilities of the S atom are not sufficiently explored. In general, due to a low electronegativity, the sulfur is rarely considered as a relevant hydrogen bonding acceptor.…”