Nitrosylation Mechanisms of Mycobacterium tuberculosis and Campylobacter jejuni Truncated Hemoglobins N, O, and P

Abstract

Truncated hemoglobins (trHbs) are widely distributed in bacteria and plants and have been found in some unicellular eukaryotes. Phylogenetic analysis based on protein sequences shows that trHbs branch into three groups, designated N (or I), O (or II), and P (or III). Most trHbs are involved in the O2/NO chemistry and/or oxidation/reduction function, permitting the survival of the microorganism in the host. Here, a detailed comparative analysis of kinetics and/or thermodynamics of (i) ferrous Mycobacterium tubertulosis trHbs N and O (Mt-trHbN and Mt-trHbO, respectively), and Campylobacter jejuni trHb (Cj-trHbP) nitrosylation, (ii) nitrite-mediated nitrosylation of ferrous Mt-trHbN, Mt-trHbO, and Cj-trHbP, and (iii) NO-based reductive nitrosylation of ferric Mt-trHbN, Mt-trHbO, and Cj-trHbP is reported. Ferrous and ferric Mt-trHbN and Cj-trHbP display a very high reactivity towards NO; however, the conversion of nitrite to NO is facilitated primarily by ferrous Mt-trHbN. Values of kinetic and/or thermodynamic parameters reflect specific trHb structural features, such as the ligand diffusion pathways to/from the heme, the heme distal pocket structure and polarity, and the ligand stabilization mechanisms. In particular, the high reactivity of Mt-trHbN and Cj-trHbP reflects the great ligand accessibility to the heme center by two protein matrix tunnels and the E7-path, respectively, and the penta-coordination of the heme-Fe atom. In contrast, the heme-Fe atom of Mt-trHbO the ligand accessibility to the heme center of Mt-trHbO needs large conformational readjustments, thus limiting the heme-based reactivity. These results agree with different roles of Mt-trHbN, Mt-trHbO, and Cj-trHbP in vivo.

Targeting Mitochondrial Dysfunction with L-Alpha Glycerylphosphorylcholine

“…Furthermore, the IR-induced increases in superoxide and hydrogen peroxide levels in the circulating blood were accompanied by increased local NOx concentrations, providing indirect evidence for the evolving oxido-nitrosative stress in the liver tissue. RNS acting together with ROS generates “footprints” of tissue damage [42]. ROS interacting with NO produces peroxynitrite [43] and nitration of mitochondrial proteins resulting in acute and chronic liver diseases.…”

NO2−-mediated nitrosylation of ferrous microperoxidase-11

“…The primary finding of this study is to highlight the role played by the coordination geometry of the heme-Fe(II) atom, the structural features of the heme cavity and/or the arrangement of barriers along the ligand pathway toward the heme pocket in the modulation of the NO 2 − reduction to NO by heme-proteins and related heme-model compounds with the concomitant formation of the ferrous nitrosylated derivative (Table 1) [21,[25][26][27]30,31,[34][35][36][37]39]. In this respect, MP-11-Fe represents a valuable heme-model compound displaying the pentacoordinated metal center instead of the hexa-coordinated heme-Featom of the parent horse heart cyt c [22].…”

“…Kinetics and thermodynamics of the NO 2 − -mediated nitrosylation of MP11-Fe(II) were analyzed in the framework of the minimum reaction mechanism depicted in Scheme 1 [21,[24][25][26][27][29][30][31][32][33][34][35][36][37][38][39].…”

“…Values of the pseudo-first-order rate constant for NO binding to MP11-Fe(II) (i.e., h) were obtained according to Eq. (3) [37]:…”

Structural determinants of ligand binding in truncated hemoglobins: Resonance Raman spectroscopy of the native states and their carbon monoxide and hydroxide complexes

“…The organisms hosting TrHbs span from pathogenic bacteria to those performing photosynthesis, fixing nitrogen or showing distinctive metabolic capabilities . Accordingly, a variety of functions have been proposed, including protection from reactive O 2 (ROS) and nitrogen (RNS) species, O 2 and NO detoxification, sulfide, nitrite, and peroxynitrite chemistry, however, the function of TrHbs remains poorly defined.…”