Stepwise nitrosylation of the nonheme iron site in an engineered azurin and a molecular basis for nitric oxide signaling mediated by nonheme iron proteins

Abstract

Mononitrosyl and dinitrosyl iron species, such as {FeNO}7, {FeNO}8 and {Fe(NO)2}9, have been proposed to play pivotal roles in the nitrosylation processes of nonheme iron centers in biological systems. Despite...

Development of Nonheme {FeNO}7 Complexes Based on the Pyrococcus furiosus Rubredoxin for Red-Light-Controllable Nitric Oxide Release

“…Interestingly, the EPR spectrum (Figures and S5) revealed the presence of two species, including a HS species of iron ( S = 3 / 2 ), with g = 4.0 (species A, ∼70%), and a low-spin (LS) species of iron ( S = 1 / 2 ), with g = 2.03 (species B, ∼30%). Species A is consistent with those observed in the MNICs with the S = 3 / 2 ground state ({FeNO} 7 ) of nonheme iron proteins and their model complexes, ,− whereas species B seems to be the well-known DNICs ({Fe­(NO) 2 } 9 ) species. , To identify the origin of the two EPR species, the nitrosylated sample was extensively washed through a PD-10 column, and the temperature-dependent EPR spectra of the resulting sample were recorded (Figure S6). While still present, both EPR signals declined gradually with no significant changes in the signal shape at higher temperatures, indicating that they are related to the protein scaffold instead of small molecular species; i.e., both species are protein-bound .…”

“…While still present, both EPR signals declined gradually with no significant changes in the signal shape at higher temperatures, indicating that they are related to the protein scaffold instead of small molecular species; i.e., both species are protein-bound . Further, the existence of two EPR species was suspected to be related to the amount of NO, as previously reported in the stepwise nitrosylation of iron–sulfur complexes, ,, converting MNICs to DNICs in the present of excess NO. With this in mind, a stepwise NO addition was carried out; however, the two species existed regardless of the amount of NO added (Figure S7).…”

Designing Artificial Metalloenzymes by Tuning of the Environment beyond the Primary Coordination Sphere

“…The PCSs of native mononuclear non-heme Fe enzymes predominately utilize the facial (His) 2 -carboxylate triad, which has served as the major inspiration for initial designs of non-heme Fe ArMs. However, despite their prevalence in nature, relatively few non-heme Fe ArMs have been designed which employ natural amino acid side chains/protein backbone for metal ion coordination, ,− , at least when compared to those for other metals such as Cu, Ni, and Zn. As a result, the study of SCS interactions in non-heme Fe ArMs has not advanced to the extent discussed in some other sections, underlining the need for continued developments in this field, particularly toward mono- and dioxygenase activity.…”

“…More recently, the Lu group has further utilized Az to engineer the formation of a dinitrosyl iron complex (DNIC) . Nitric oxide (NO) plays an important role in numerous processes ranging from cellular signaling to immune defense, and understanding how these processes are regulated by non-heme Fe proteins remains an intense subject of investigation.…”

“…More recently, the Lu group has further utilized Az to engineer the formation of a dinitrosyl iron complex (DNIC). 274 Nitric oxide (NO) plays an important role in numerous processes ranging from cellular signaling to immune defense, and understanding how these processes are regulated by nonheme Fe proteins remains an intense subject of investigation. Note that in the following we will use Enemark−Feltham notation, {MNO} n , to describe the overall oxidation state of NO-bound metal (M) systems, where n denotes the number of valence electrons (metal d plus NO π* electrons).…”