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The self‐organization of microbes into biofilms provides multiple benefits including tolerance to mechanical stress and resistance to immune defences and antibiotics. Coupled to a compromised mucociliary function, these traits have dire consequences in cystic fibrosis patients – persistent infections are the main reason for morbidity and mortality. Thereby, disease progression is associated with universal colonization by Pseudomonas aeruginosa, which selects for a slimy phenotype to adapt to the lung microenvironment. Recognizing this, drug‐delivery vehicles that break down the mucoid extracellular matrix made of alginate are designed to enable better penetration and biofilm dispersion. In parallel, a protective layer responds to the proteolytic activity of the pathogen and thus controls drug availability. To realize this architecture, silica nanoparticles are loaded with imipenem, and then coated with elastin and alginate lyase in a layer‐by‐layer fashion using ultrasound. The nanoscale formulations eradicate up to 80% of the total biomass and reduce the bacterial viability in biofilms by 3 logs, considerably outperforming the bulk antibiotic in vitro, whereby the effects are correlated to changes in the viscoelasticity. Furthermore, the stimuli‐responsive nanocarriers are safe and effective in animal models of P. aeruginosa infection, presenting a considerable therapeutic promise in the challenging context of lung diseases. [ABSTRACT FROM AUTHOR]

Retinitis pigmentosa (RP) is a group of genetically and clinically heterogeneous inherited degenerative retinopathies caused by abnormalities of photoreceptors or retinal pigment epithelium in the retina leading to progressive sight loss. Rhodopsin is the prototypical G-protein-coupled receptor located in the vertebrate retina and is responsible for dim light vision. Here, novel M39R and N55K variants were identified as causing an intriguing sector phenotype of RP in affected patients, with selective degeneration in the inferior retina. To gain insights into the molecular aspects associated with this sector RP phenotype, whose molecular mechanism remains elusive, the mutations were constructed by site-directed mutagenesis, expressed in heterologous systems, and studied by biochemical, spectroscopic, and functional assays. M39R and N55K opsins had variable degrees of chromophore regeneration when compared with WT opsin but showed no gross structural misfolding or altered trafficking. M39R showed a faster rate for transducin activation than WT rhodopsin with a faster metarhodopsinII decay, whereas N55K presented a reduced activation rate and an altered photobleaching pattern. N55K also showed an altered retinal release from the opsin binding pocket upon light exposure, affecting its optimal functional response. Our data suggest that these sector RP mutations cause different protein phenotypes that may be related to their different clinical progression. Overall, these findings illuminate the molecular mechanisms of sector RP associated with rhodopsin mutations.

Trace metals are essential elements that play key roles in a number of biochemical processes governing human visual physiology in health and disease. Several trace metals, such as zinc, have been shown to play important roles in the visual phototransduction process. In spite of this, there has been little research conducted on the direct effect of trace metal elements on the visual photoreceptor rhodopsin. In the current study, we have determined the effect of several metal ions, such as iron, copper, chromium, manganese, and nickel, on the conformational stability of rhodopsin. To this aim, we analyzed, by means of UV-visible and fluorescence spectroscopic methods, the effects of these trace elements on the thermal stability of dark rhodopsin, the stability of its active Metarhodopsin II conformation, and its chromophore regeneration. Our results show that copper prevented rhodopsin regeneration and slowed down the retinal release process after illumination. In turn, Fe3+, but not Fe2+, increased the thermal stability of the dark inactive conformation of rhodopsin, whereas copper ions markedly decreased it. These findings stress the important role of trace metals in retinal physiology at the photoreceptor level and may be useful for the development of novel therapeutic strategies to treat retinal disease. [ABSTRACT FROM AUTHOR]

High-resolution NMR methods were used to study the interaction between light-activated rhodopsin and the retinal G-protein transducin (G1) as a model system to probe for conformational changes in the G[alpha] subunit accompanying signal propagation from R* to the G-protein. The results suggest that changes in the extreme amino and carboxyl termini of G[alpha] that are thought to occur upon interaction with R*, rather than the absence of bound guanine nucleotide, are the predominant factors which govern G[alpha] conformation and dynamics in the R*- bound empty pocket state.

Mutations in the visual photoreceptor rhodopsin are the cause of the retinal degenerative disease retinitis pigmentosa. Some naturally occurring mutations 100 can lead to protein conformational instability. Two such mutations, N55K and G90V, 80 in the first and second transmembrane helices of the receptor, have been associated with sector and classical retinitis pigmentosa, respectively, and showed enhanced