2025 · International journal of molecular sciences · MDPI · added 2026-04-21
Reactive molecules, including oxygen and nitrogen species, serve dual roles in human physiology. While they function as essential signaling molecules under normal physiological conditions, they contri Show more
Reactive molecules, including oxygen and nitrogen species, serve dual roles in human physiology. While they function as essential signaling molecules under normal physiological conditions, they contribute to cellular dysfunction and damage when produced in excess by normal metabolism or in response to stressors. Oxidative/nitrosative stress is a pathological state, resulting from the overproduction of reactive species exceeding the antioxidant capacity of the body, which is implicated in several chronic human diseases. Antioxidant Show less
2019 · · American Society for Biochemistry and Molecular Biology · added 2026-04-20
Iron is critical for virtually all organisms, yet major questions remain regarding the systems-level understanding of iron in whole cells. Here, we obtained Mössbauer and EPR spectra of Escherichia Show more
Iron is critical for virtually all organisms, yet major questions remain regarding the systems-level understanding of iron in whole cells. Here, we obtained Mössbauer and EPR spectra of Escherichia coli cells prepared under different nutrient iron concentrations, carbon sources, growth phases, and O2 concentrations to better understand their global iron content. We investigated WT cells and those lacking Fur, FtnA, Bfr, and Dps proteins. The coarse-grain iron content of exponentially growing cells consisted of iron-sulfur clusters, variable amounts of nonheme high-spin FeII species, and an unassigned residual quadrupole doublet. The iron in stationary-phase cells was dominated by magnetically ordered FeIII ions due to oxyhydroxide nanoparticles. Analysis of cytosolic extracts by size-exclusion chromatography detected by an online inductively coupled plasma mass spectrometer revealed a low-molecular-mass (LMM) FeII pool consisting of two iron complexes with masses of ∼500 (major) and ∼1300 (minor) Da. They appeared to be high-spin FeII species with mostly oxygen donor ligands, perhaps a few nitrogen donors, and probably no sulfur donors. Surprisingly, the iron content of E. coli and its reactivity with O2 were remarkably similar to those of mitochondria. In both cases, a "respiratory shield" composed of membrane-bound iron-rich respiratory complexes may protect the LMM FeII pool from reacting with O2 When exponentially growing cells transition to stationary phase, the shield deactivates as metabolic activity declines. Given the universality of oxidative phosphorylation in aerobic biology, the iron content and respiratory shield in other aerobic prokaryotes might be similar to those of E. coli and mitochondria. Show less
We investigated the effects of a crowded environment on guanine oxidation in pyrene-modified oligonucleotides by photoinduced electron transfer. We observed drastic promotion of guanine oxidation in Ψ Show more
We investigated the effects of a crowded environment on guanine oxidation in pyrene-modified oligonucleotides by photoinduced electron transfer. We observed drastic promotion of guanine oxidation in Ψ (psi; polymer- and salt-induced)-type DNA. Show less
Cytochrome c binds to cardiolipin (CL) on the inner mitochondrial membrane during the initial stages of apoptosis where it oxidizes CL, promoting its release into the cytoplasm where it initiates apop Show more
Cytochrome c binds to cardiolipin (CL) on the inner mitochondrial membrane during the initial stages of apoptosis where it oxidizes CL, promoting its release into the cytoplasm where it initiates apoptosis. Previous work has identified interaction sites on cytochrome c involved in the cytochrome c-CL interaction. The contributions of the lysines attributed to site A, the anionic site, are studied here to elucidate the relative importance of each for electrostatic interaction of cytochrome c with CL at pH 8, conditions where site A is dominant. A set of single, double, and quadruple lysine to alanine variants of yeast iso-1-cytochrome c, at sequence positions 72, 73, 86, and 87, show that all contribute to the site A-mediated interaction with CL. All variants experience two sequential structural rearrangements as the lipid to protein ratio (LPR) increases. At a low LPR near 10, all variants undergo a small heme-centered structural change detected by Soret circular dichroism. At higher LPRs ranging from 22 to 34, all variants partially unfold as detected by Trp59 emission. The robustness of the mechanism of interaction to sequential neutralization of the four lysines assigned to site A demonstrates that site A is more extensive than previously supposed. The nature of both structural rearrangements also depends on which lysines constitute site A. The peroxidase activity of cytochrome c in the early stages of apoptosis depends on the nature of structural rearrangement near the heme. Thus, the lysines that comprise site A may have evolved to optimize the peroxidase signaling switch. Show less