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F1FO ATP synthase molecular motor mechanisms
The F-ATP synthase, consisting of F1 and FO motors connected by a central rotor and the stators, is the enzyme responsible for synthesizing the majority of ATP in all organisms. The F1 (αβ)3 ring stator contains three catalytic sites. Single-molecule F1 rotation studies revealed that ATP hydrolysis at each catalytic site (0°) precedes a power-stroke that rotates subunit-γ 120° with angular velocities that vary with rotational position. Catalytic site conformations vary relative to subunit-γ position (βE, empty; βD, ADP bound; βT, ATP-bound). During a power stroke, βE binds ATP (0°–60°) and βD releases ADP (6...
Source: Frontiers in Microbiology - August 23, 2022 Category: Microbiology Source Type: research

Structures of the ATP-fueled ClpXP proteolytic machine bound to protein substrate
We present cryo-EM studies of theE. coli enzyme that show how asymmetric hexameric rings of ClpX bind symmetric heptameric rings of ClpP and interact with protein substrates. Subunits in the ClpX hexamer assume a spiral conformation and interact with two-residue segments of substrate in the axial channel, as observed for other AAA+ proteases and protein-remodeling machines. Strictly sequential models of ATP hydrolysis and a power stroke that moves two residues of the substrate per translocation step have been inferred from these structural features for other AAA+ unfoldases, but biochemical and single-molecule biophysical ...
Source: eLife - February 28, 2020 Category: Biomedical Science Tags: Structural Biology and Molecular Biophysics Source Type: research

Challenge to the Intestinal Mucosa During Sepsis
Conclusion The impact of sepsis on the gut is manifold, e.g., sepsis mediated alteration of the gut-blood barrier and increase in the intestinal permeability, which may correlate with the phenomena of bacterial translocation and lymphatic activation (“toxic-lymph”). Systemic consequences of sepsis are widespread and concern to the coagulative system, the microbiome as well as enzymes, such as pancreatic proteases, MMPs and IAPs. Nevertheless, the therapeutic approaches for modulating the mucosal immune system are still rarely effective in daily routine. Recent published studies showing that treatment with ...
Source: Frontiers in Immunology - April 29, 2019 Category: Allergy & Immunology Source Type: research

Plant-Derived Alkaloids: The Promising Disease-Modifying Agents for Inflammatory Bowel Disease
Conclusion This paper summarizes the current findings regarding the anti-colitis activity of plant-derived alkaloids and shows how these alkaloids exhibit significant and beneficial effects in alleviating colonic inflammation. These natural alkaloids are not only promising agents for IBD treatment but are also components for developing new wonder drugs. However, the underlying molecular mechanisms or toxicological evaluation of most plant-derived alkaloids still require much scientific research, and their actual efficacies for IBD patients have not been verified well in field research. Thus, further clinical trials to elu...
Source: Frontiers in Pharmacology - April 11, 2019 Category: Drugs & Pharmacology Source Type: research