État natif (biochimie)

Résumé

vignette|Cys and Arg active site of ubiquitin activating enzyme. En biochimie, l'état natif d'une protéine est sa forme fonctionnelle ou opérative. Toutes les molécules de protéines sont des chaines linéaires d'acides aminés, mais c'est au moyen de leurs formes tridimensionnelles qu'elles sont capables de jouer leurs rôles biologiques. Les modifications de formes des protéines sont les causes primaires de maladies neurodégénératives, y compris celles causées par les prions ou encore l'amylose. De nombreuses enzymes et d'autres protéines non-structurales ont plus d'un état natif, et elles agissent ou sont régulées par des transitions entre ces états. Cependant, l'expression est utilisée quasi exclusivement au singulier, typiquement afin de distinguer de manière nette les protéines repliées des protéines dénaturées ou des protéines non-repliées. Dans d'autres contextes, la forme repliée d'une protéine est la plupart du temps désignée comme sa ou sa . Les protéines repliées ou dépliée

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https://fr.wikipedia.org/wiki/%C3%89tat_natif_(biochimie)

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Introduction to the application of the notions and methods of theoretical physics to problems in biology.

In this course we will study the cell (minimum unit of life) and its components. We will study several key cellular features: Membranes, genomes, channels and receptors. We will apply the laws of physics to develop models to make quantitative and predictive statements.

Les constituants biochimiques de l'organisme, protéines, glucides, lipides, à la lumière de l'évolution des concepts et des progrès en biologie moléculaire et génétique, sont étudiés.

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Nanocarriers, including liposomes, offer great opportunities for targeted and controlled therapy. The development in this field has led to a large panel of drug delivery systems, which can be classified into 3 different nanovector generations. However, the success of such smart materials requires the control of a large variety of properties and parameters. Unfortunately, characterization at the nanoscale is often cumbersome and many methods are still being developed. Liposomes have been characterized by cryogenic electron microscopy (CryoTEM) for quite some time, also in combination with nanoparticles, in particular with superparamagnetic iron oxide nanoparticles (SPIONs) incorporated inside the liposomal membrane. CryoTEM, unlike classical TEM, maintains the native state of the liposomes. The quick freezing of the sample immobilizes particles and liposomes exactly at their position in the suspension. Therefore, localization information can be extracted from the images. However, data must be treated extremely carefully keeping in mind that 2-D projections of a 3-D object are observed. In this paper, we discuss the analysis of cryoTEM images of liposome-particle hybrids, including the estimation of the contrast transfer function (CTF) and electron dose, as well as the correct positioning of the sample holder and tomography for accurate localization.

Ieee-Inst Electrical Electronics Engineers Inc2013

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A fluorescent multi-domain protein reveals the unfolding mechanism of Hsp70

Salvatore Assenza, Paolo De Los Rios, Bruno Claude Daniel Fauvet, Pierre Goloubinoff

Detailed understanding of the mechanism by which Hsp70 chaperones protect cells against protein aggregation is hampered by the lack of a comprehensive characterization of the aggregates, which are typically heterogeneous. Here we designed a reporter chaperone substrate, MLucV, composed of a stress-labile luciferase flanked by stress-resistant fluorescent domains, which upon denaturation formed a discrete population of small aggregates. Combining Forster resonance energy transfer and enzymatic activity measurements provided unprecedented details on the aggregated, unfolded, Hsp70-bound and native MLucV conformations. The Hsp70 mechanism first involved ATP-fueled disaggregation and unfolding of the stable pre-aggregated substrate, which stretched MLucV beyond simply unfolded conformations, followed by native refolding. The ATP-fueled unfolding and refolding action of Hsp70 on MLucV aggregates could accumulate native MLucV species under elevated denaturing temperatures highly adverse to the native state. These results unambiguously exclude binding and preventing of aggregation from the non-equilibrium mechanism by which Hsp70 converts stable aggregates into metastable native proteins.

NATURE PORTFOLIO2022

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Chaperones convert the energy from ATP into the nonequilibrium stabilization of native proteins

Alessandro Barducci, Paolo De Los Rios, Bruno Claude Daniel Fauvet, Pierre Goloubinoff, Alberto Stefano Sassi

During and after protein translation, molecular chaperones require ATP hydrolysis to favor the native folding of their substrates and, under stress, to avoid aggregation and revert misfolding. Why do some chaperones need ATP, and what are the consequences of the energy contributed by the ATPase cycle? Here, we used biochemical assays and physical modeling to show that the bacterial chaperones GroEL (Hsp60) and DnaK (Hsp70) both use part of the energy from ATP hydrolysis to restore the native state of their substrates, even under denaturing conditions in which the native state is thermodynamically unstable. Consistently with thermodynamics, upon exhaustion of ATP, the metastable native chaperone products spontaneously revert to their equilibrium non-native states. In the presence of ATPase chaperones, some proteins may thus behave as open ATP-driven, nonequilibrium systems whose fate is only partially determined by equilibrium thermodynamics.

2018

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