Resolution of Key Roles for the Distal Pocket Histidine in Cytochrome c Nitrite Reductases

Cytochrome c nitrite reductases perform a key step in the biogeochemical N-cycle by catalyzing the six-electron reduction of nitrite to ammonium. These multi-heme cytochromes contain a number of His/His ligated c-hemes for electron transfer and a structurally differentiated heme that provides the catalytic center. The catalytic heme has proximal ligation from lysine, or histidine, and an exchangeable distal ligand bound within a pocket that includes a conserved histidine. Here we describe properties of a penta-heme cytochrome c nitrite reductase in which the distal His has been substituted by Asn. The variant is unable to catalyze nitrite reduction despite retaining the ability to reduce a proposed intermediate in that process, namely, hydroxylamine. A combination of electrochemical, structural and spectroscopic studies reveals that the variant enzyme simultaneously binds nitrite and electrons at the catalytic heme. As a consequence the distal His is proposed to play a key role in orienting the nitrite for N-O bond cleavage. The electrochemical experiments also reveal that the distal His facilitates rapid nitrite binding to the catalytic heme of the native enzyme. Finally it is noted that the thermodynamic descriptions of nitrite- and electron-binding to the active site of the variant enzyme are modulated by the prevailing oxidation states of the His/His ligated hemes. This is behavior that is likely to be displayed by other multi-centered redox enzymes such that there are wide implications for considering the determinants of catalytic activity in this important and varied group of oxidoreductases

Discovering Body Positivity & Self-Image (Gender Equality Coalition of Ontario)

Body image refers to the way we perceive our bodies, and it can positively or negatively impact physical and mental health (Alleva et al., 2015). Unfortunately, negative body image is becoming more common with some studies finding that 65% of young people are dissatisfied with their bodies (Linardon et al., 2021). This can lead to a variety of psychological and behavioral problems and disorders such as body dysmorphia or eating disorders (Alleva et al., 2015). However, many of these consequences associated with negative body image can be circumvented by learning to foster positive body images through building self-esteem (Jessie’s Legacy, 2017). In partnership with the Gender Equality Coalition of Ontario, we have developed a two-part Discovering Body Positivity and Self-Image workshop that will be offered to the London community online in a mentor-mentee setting. The goal is to enable people of different ages, races, and genders to identify negative self-concepts about their body image and learn strategies to promote a positive body image as well as coping mechanisms for resilience

A research methodology study to map the process of initiating and operating a randomised controlled trial of podoconiosis treatment in Northern Ethiopia

No description supplie

Interleukin-1α Activity in Necrotic Endothelial Cells Is Controlled by Caspase-1 Cleavage of Interleukin-1 Receptor-2: IMPLICATIONS FOR ALLOGRAFT REJECTION.

Inflammation is a key instigator of the immune responses that drive atherosclerosis and allograft rejection. IL-1α, a powerful cytokine that activates both innate and adaptive immunity, induces vessel inflammation after release from necrotic vascular smooth muscle cells (VSMCs). Similarly, IL-1α released from endothelial cells (ECs) damaged during transplant drives allograft rejection. However, IL-1α requires cleavage for full cytokine activity, and what controls cleavage in necrotic ECs is currently unknown. We find that ECs have very low levels of IL-1α activity upon necrosis. However, TNFα or IL-1 induces significant levels of active IL-1α in EC necrotic lysates without alteration in protein levels. Increased activity requires cleavage of IL-1α by calpain to the more active mature form. Immunofluorescence and proximity ligation assays show that IL-1α associates with interleukin-1 receptor-2, and this association is decreased by TNFα or IL-1 and requires caspase activity. Thus, TNFα or IL-1 treatment of ECs leads to caspase proteolytic activity that cleaves interleukin-1 receptor-2, allowing IL-1α dissociation and subsequent processing by calpain. Importantly, ECs could be primed by IL-1α from adjacent damaged VSMCs, and necrotic ECs could activate neighboring normal ECs and VSMCs, causing them to release inflammatory cytokines and up-regulate adhesion molecules, thus amplifying inflammation. These data unravel the molecular mechanisms and interplay between damaged ECs and VSMCs that lead to activation of IL-1α and, thus, initiation of adaptive responses that cause graft rejection.This study was supported by British Heart Foundation Grants FS/09/005/26845, FS/13/3/30038 and FS/11/77/29327 (MCHC) & RG/13/14/30314 (MRB); the BHF Cambridge CRE; and the NIHR Cambridge BRC.This is the final version of the article. It first appeared from ASBMB via http://dx.doi.org/10.1074/jbc.M115.66791