Global S&T Development Trend Analysis Platform of Resources and Environment
TWIK-related acid-sensitive potassium (TASK) channels-members of the two pore domain potassium (K-2P) channel family-are found in neurons(1), cardiomyocytes(2-4) and vascular smooth muscle cells(5), where they are involved in the regulation of heart rate(6), pulmonary artery tone(5,7), sleep/wake cycles(8) and responses to volatile anaesthetics(8-11). K-2P channels regulate the resting membrane potential, providing background K+ currents controlled by numerous physiological stimuli(12-15). Unlike other K-2P channels, TASK channels are able to bind inhibitors with high affinity, exceptional selectivity and very slow compound washout rates. As such, these channels are attractive drug targets, and TASK-1 inhibitors are currently in clinical trials for obstructive sleep apnoea and atrial fibrillation(16). In general, potassium channels have an intramembrane vestibule with a selectivity filter situated above and a gate with four parallel helices located below
The X-ray crystal structure of the potassium channel TASK-1 reveals the presence of an X-gate, which traps small-molecule inhibitors in the intramembrane vestibule and explains their low washout rates from the channel.
The authors report near-atomic resolution structures of the R-type bacteriocin from Pseudomonas aeruginosa in the pre-contraction and post-contraction states, and these structures provide insight into the mechanism of action of molecular syringes.
R-type bacteriocins are minimal contractile nanomachines that hold promise as precision antibiotics(1-4). Each bactericidal complex uses a collar to bridge a hollow tube with a contractile sheath loaded in a metastable state by a baseplate scaffold(1,2). Fine-tuning of such nucleic acid-free protein machines for precision medicine calls for an atomic description of the entire complex and contraction mechanism, which is not available from baseplate structures of the (DNA-containing) T4 bacteriophage(5). Here we report the atomic model of the complete R2 pyocin in its pre-contraction and post-contraction states, each containing 384 subunits of 11 unique atomic models of 10 gene products. Comparison of these structures suggests the following sequence of events during pyocin contraction: tail fibres trigger lateral dissociation of baseplate triplexes
Various species of the intestinal microbiota have been associated with the development of colorectal cancer(1,2), but it has not been demonstrated that bacteria have a direct role in the occurrence of oncogenic mutations. Escherichia coli can carry the pathogenicity island pks, which encodes a set of enzymes that synthesize colibactin(3). This compound is believed to alkylate DNA on adenine residues(4,5) and induces double-strand breaks in cultured cells(3). Here we expose human intestinal organoids to genotoxic pks(+)E. coli by repeated luminal injection over five months. Whole-genome sequencing of clonal organoids before and after this exposure revealed a distinct mutational signature that was absent from organoids injected with isogenic pks-mutant bacteria. The same mutational signature was detected in a subset of 5,876 human cancer genomes from two independent cohorts, predominantly in colorectal cancer. Our study describes a distinct mutational signature in colorectal cancer and implies that the underlying mutational process results directly from past exposure to bacteria carrying the colibactin-producing pks pathogenicity island.
Organoids derived from human intestinal cells that are co-cultured with bacteria carrying the genotoxic pks(+) island develop a distinct mutational signature associated with colorectal cancer.
Protein structure prediction can be used to determine the three-dimensional shape of a protein from its amino acid sequence(1). This problem is of fundamental importance as the structure of a protein largely determines its function(2)