Membrane protein assembly patterns reflect selection for non-proliferative structures

AbstractMembrane proteins that regulate solute movement are often built from multiple copies of an identical polypeptide chain. These complexes represent striking examples of self-assembling systems that recruit monomers only until a prescribed level for function is reached. Here we report that three modes of assembly – distinguished by sequence and stoichiometry – describe all helical membrane protein complexes currently solved to high resolution. Using the 13 presently available non-redundant homo-oligomeric structures, we show that two of these types segregate with protein function: one produces energy-dependent transporters, while the other builds channels for passive diffusion. Given such limited routes to functional complexes, membrane proteins that self-assemble exist on the edge of aggregation, susceptible to mutations that may underlie human diseases

Propuesta de protocolo para la identificación y evaluación de barreras arquitectònicas en situaciones de evacuación, en edificios de uso público

Para el desarrollo del trabajo hemos elaborado un protocolo con la finalidad de poder ser utilizado como checklist. Éste, está destinado para utilizarse en edificios de uso público, y ayudar a identificar las barreras arquitectónicas de manera rápida y cómoda, tanto en situación de uso normal como en situación de evacuación. Una parte ha sido elaborada con la legislación vigente y la otra con bibliografía especializada, junto con los técnicos especializados y agentes implicados. Las normativas aplicadas han sido por un lado, la correspondiente a nivel autonómico de Catalunya y por otro, las de nivel estatal. Las hemos examinado de manera cronológica analizando así su evolución en el tiempo. Con el fin de tener en cuenta el punto de vista de los agentes implicados, nos hemos reunido con el Departamento de Bomberos de Barcelona. Nos interesaba conocer su experiencia profesional para analizar la problemática con la que ellos se encuentran y saber su opinión con respecto a la normativa vigente. El hecho de entrevistarnos con los colectivos de minusválidos le da un valor añadido, porque aunque, en su mayoría no son técnicos, si que conocen las deficiencias que tienen los edificios de primera mano y, sobre todo, que opinan ellos que se debería mejorar, tanto a nivel legislativo como educativo. Con todos estos puntos de vista, hemos elaborado a través del checklist, una manera rápida y eficaz de identificar las barreras arquitectónicas de un edificio de uso público. Una vez elaborado el protocolo, hemos querido dar un paso más allá, poniéndolo en práctica en dos edificios y así comprobar la eficacia del mismo. Con los resultados obtenidos en la validación del protocolo, hemos concluido el trabajo con la incorporación de mejoras a las deficiencias. Lo que nos ha llevado a formarnos en el asesoramiento técnico sobre supresión de barreras arquitectónicas. Precisando de la investigación de industriales del sector (especializados y colaboradores de entes como el CEAPAT, ONCE, etc.), para conocer la innovación en sistemas existentes en el mercad

Defining the Defect in F508 del CFTR: A Soluble Problem?

Previously reported crystal structures of CFTR F508 del-NBD1 were determined in the presence of solubilizing mutations. In this issue of Chemistry & Biology, Pissarra et al. (2008) show that partial rescue of the trafficking and gating defects of full-length CFTR occurs in vivo upon recapitulation of the solubilizing F494N/Q637R or F428S/F494N/Q637R substitutions in cis with F508 del

Seeking Accountability: Multi-Service Accountability Agreements (MSAAs) in Ontario’s Community Support Sector

Multi-Service Accountability Agreements (MSAAs) have been put in place to hold Community Sector Service (CSS) agencies to account for services receiving public funding in Ontario. The MSAA seeks to support financial and performance accountability, requiring CSS agencies to report on their performance quarterly. The MSAA is an expenditure policy tool that has undergone several iterations, each informed by negotiations between the Ontario Ministry of Health and Long-Term Care (MOHLTC), the province’s regional authorities—known as Local Health Integration Networks (LHINs)—and organizations/associations representing CSS agency interests. This approach to accountability is consistent with a broader focus on the government role as ‘steering’ service delivery rather than ‘rowing.’ The MSAA offers a standardized, politically acceptable approach to accountability. However, the MSAA relies heavily on performance indicators that may not adequately reflect quality care. The MSAA exemplifies the tension between the need for strong standardized accountability requirements for publicly-funded health service providers and the need for services that meet the needs of their communities

Arenas de conflito em torno do cuidado

The text explores the arenas of conflict surrounding care in rest homes. Technical teams, carers and elderly dependents constitute a specific configuration of life in these institutions. Here I analyse the way in which Pascale Molinier approaches the topic in her article "Intersectionality, care and feminism," providing a counterpoint through my research on immigrant women who care for the elderly in Italy and domestic work in Brazil.O texto explora as arenas de conflito em torno do cuidado em asilos. Equipe técnica, cuidadoras e idosos dependentes constituem uma configuração específica da vida nessas instituições. Trata-se de analisar o modo pelo qual a questão é abordada por Pascal Molinier no artigo "Interseccionalidade, cuidado e feminismo", tendo como contraponto minha pesquisa sobre mulheres imigrantes cuidadoras de idosos na Itália e o emprego doméstico no Brasil

Heat treatment of thioredoxin fusions increases the purity of α-helical transmembrane protein constructs.

Membrane proteins play key roles in cellular signaling and transport, represent the majority of drug targets, and are implicated in many diseases. Their relevance renders them important subjects for structural, biophysical, and functional investigations. However, obtaining membrane proteins in high purities is often challenging with conventional purification steps alone. To address this issue, we present here an approach to increase the purity of α-helical transmembrane proteins. Our approach exploits the Thioredoxin (Trx) tag system, which is able to confer some of its favorable properties, such as high solubility and thermostability, to its fusion partners. Using Trx fusions of transmembrane helical hairpin constructs derived from the human cystic fibrosis transmembrane conductance regulator (CFTR) and a bacterial ATP synthase, we establish conditions for the successful implementation of the selective heat treatment procedure to increase sample purity. We further examine systematically its efficacy with respect to different incubation times and temperatures using quantitative gel electrophoresis. We find that minute-timescale heat treatment of Trx-tagged fusion constructs with temperatures ranging from 50 to 90°C increases the purity of the membrane protein samples from ~60 to 98% even after affinity purification. We show that this single-step approach is even applicable in cases where regular selective heat purification from crude extracts, as reported for Trx fusions to soluble proteins, fails. Overall, our approach is easy to integrate into existing purification strategies and provides a facile route for increasing the purity of membrane protein constructs after purification by standard chromatography approaches

Бесплатный обязательный экземпляр полиграфических и других изданий как один из источников комплектования Латвийской академической библиотеки

Aggregation of amyloid beta (Aβ) into oligomers and fibrils is believed to play an important role in the development of Alzheimer's disease (AD). To gain further insight into the principles of aggregation, we have investigated the induction of β-sheet secondary conformation from disordered native peptide sequences through lipidation, in 1-2% hexafluoroisopropanol (HFIP) in phosphate buffered saline (PBS). Several parameters, such as type and number of lipid chains, peptide sequence, peptide length and net charge, were explored keeping the ratio peptide/HFIP constant. The resulting lipoconjugates were characterized by several physico-chemical techniques: Circular Dichroism (CD), Attenuated Total Reflection InfraRed (ATR-IR), Thioflavin T (ThT) fluorescence, Dynamic Light Scattering (DLS), solid-state Nuclear Magnetic Resonance (ssNMR) spectroscopy and Electron Microscopy (EM). Our data demonstrate the generation of β-sheet aggregates from numerous unstructured peptides under physiological pH, independent of the amino acid sequence. The amphiphilicity pattern and hydrophobicity of the scaffold were found to be key factors for their assembly into amyloid-like structures

Deciphering the folding kinetics of transmembrane helical proteins

Nearly a quarter of genomic sequences and almost half of all receptors that are likely to be targets for drug design are integral membrane proteins. Understanding the detailed mechanisms of the folding of membrane proteins is a largely unsolved, key problem in structural biology. Here, we introduce a general model and use computer simulations to study the equilibrium properties and the folding kinetics of a $C_{\alpha}$-based two helix bundle fragment (comprised of 66 amino-acids) of Bacteriorhodopsin. Various intermediates are identified and their free energy are calculated toghether with the free energy barrier between them. In 40% of folding trajectories, the folding rate is considerably increased by the presence of non-obligatory intermediates acting as traps. In all cases, a substantial portion of the helices is rapidly formed. This initial stage is followed by a long period of consolidation of the helices accompanied by their correct packing within the membrane. Our results provide the framework for understanding the variety of folding pathways of helical transmembrane proteins