CRAFTing Delivery of Membrane Proteins into Protocells using Nanodiscs

For the successfulgenerativeengineeringof functionalartificialcells,a convenientandcontrollablemeansof deliveringmembraneproteinsinto membranelipidbilayersis necessary.Herewereporta deliverysystemthatachievesthis by employingmembraneprotein-carryingnanodiscsandthecalcium-dependentfusionofphosphatidylserinelipidmembranes.We showthat lipidnanodiscscanfuse a transportedlipidbilayerwith the lipidbilayersof smallunilamellarvesicles(SUVs)or giantunilamellarvesicles(GUVs)whileavoidingrecipientvesiclesaggregation.Thisis triggeredby a simple,transientincreasein calciumconcentration,whichresultsin efficientand rapidfusionin a one-potreaction.Furthermore,nanodiscscan be loadedwithmembraneproteinsthatcan be deliveredintotargetSUVor GUVmembranesin a detergent-independentfashionwhileretainingtheirfunctionality.Nanodiscshavea provenabilityto carrya widerangeof membraneproteins,controltheiroligomericstate,and arehighlyadaptable.Giventhis, our approachmay be the basisfor the developmentof usefultoolsthat will allowbespokedeliveryofmembraneproteinsto protocells,equippingthemwith the cell-likeabilityto exchangematerialacrossouter/subcellularmembranes

Efficacy and safety of endoscopic submucosal dissection for gastric tube cancer: A multicenter retrospective study

BACKGROUND Recent improvements in the prognosis of patients with esophageal cancer have led to the increased occurrence of gastric tube cancer (GTC) in the reconstructed gastric tube. However, there are few reports on the treatment results of endoscopic submucosal dissection (ESD) for GTC. AIM To evaluate the efficacy and safety of ESD for GTC after esophagectomy in a multicenter trial. METHODS We retrospectively investigated 48 GTC lesions in 38 consecutive patients with GTC in the reconstructed gastric tube after esophagectomy who had undergone ESD between January 2005 and December 2019 at 8 institutions participating in the Okayama Gut Study group. The clinical indications of ESD for early gastric cancer were similarly applied for GTC after esophagectomy. ESD specimens were evaluated in 2-mm slices according to the Japanese Classification of Gastric Carcinoma with curability assessments divided into curative and non-curative resection based on the Gastric Cancer Treatment Guidelines. Patient characteristics, treatment results, clinical course, and treatment outcomes were analyzed. RESULTS The median age of patients was 71.5 years (range, 57-84years), and there were 34 men and 4 women. The median observation period after ESD was 884 d (range, 8-4040 d). The median procedure time was 81 min (range, 29-334 min), the en bloc resection rate was 91.7% (44/48), and the curative resection rate was 79% (38/48). Complications during ESD were seen in 4% (2/48) of case, and those after ESD were seen in 10% (5/48) of case. The survival rate at 5 years was 59.5%. During the observation period after ESD, 10 patients died of other diseases. Although there were differences in the procedure time between institutions, a multivariate analysis showed that tumor size was the only factor associated with prolonged procedure time. CONCLUSION ESD for GTC after esophagectomy was shown to be safe and effective

Effects of active site residues of 3α-hydroxysteroid dehydrogenase from <i>pseudomonas</i> sp. b-0831 on its catalysis and cofactor binding

<p>We overexpressed and purified 3α-hydroxysteroid dehydrogenase from <i>Pseudomonas</i> sp. B-0831 (Ps3αHSD) and its mutants where the active site residues known as the SYK triad, Ser114, Tyr153, and Lys157, were mutated. Ps3αHSD catalyzes the reaction by using a nucleotide cofactor. The NADH binding affinity of K157A mutant was much lower than that of the wild-type, mainly due to loss of a hydrogen bond. The decreased affinity would result in decreased <i>k</i>_cat. Compared to the wild-type, the mutants S114A and Y153F showed higher <i>K</i>_m and lower <i>k</i>_cat values in both oxidation and reduction reactions. Simultaneous mutation of S114A and Y153F resulted in a significant decrease in <i>k</i>_cat relative to the single mutant. These results are supported by the notion that Tyr153 is a catalytic base and Ser114 would be a substitute. Loss of hydrogen bonding with NADH upon the Y153F mutation resulted in increased enthalpy change, partially compensated by increased entropy change.</p> <p>Crystal structure of Ps3aHSD and ITC profile for NADH binding. The effects of mutations on catalysis and cofactor binding are well correlated with the structural information.</p

Cyclic Ion Mobility for Hydrogen/Deuterium Exchange-Mass Spectrometry Applications

Hydrogen/deuterium exchange-mass spectrometry (HDX-MS) has emerged as a powerful tool to probe protein dynamics. As a bottom-up technique, HDX-MS provides information at peptide-level resolution, allowing structural localization of dynamic changes. Consequently, the HDX-MS data quality is largely determined by the number of peptides that are identified and monitored after deuteration. Integration of ion mobility (IM) into HDX-MS workflows has been shown to increase the data quality by providing an orthogonal mode of peptide ion separation in the gas phase. This is of critical importance for challenging targets such as integral membrane proteins (IMPs), which often suffer from low sequence coverage or redundancy in HDX-MS analyses. The increasing complexity of samples being investigated by HDX-MS, such as membrane mimetic reconstituted and in vivo IMPs, has generated need for instrumentation with greater resolving power. Recently, Giles et al. developed cyclic ion mobility (cIM), an IM device with racetrack geometry that enables scalable, multipass IM separations. Using one-pass and multipass cIM routines, we use the recently commercialized SELECT SERIES Cyclic IM spectrometer for HDX-MS analyses of four detergent solubilized IMP samples and report its enhanced performance. Furthermore, we develop a novel processing strategy capable of better handling multipass cIM data. Interestingly, use of one-pass and multipass cIM routines produced unique peptide populations, with their combined peptide output being 31 to 222% higher than previous generation SYNAPT G2-Si instrumentation. Thus, we propose a novel HDX-MS workflow with integrated cIM that has the potential to enable the analysis of more complex systems with greater accuracy and speed.</p

The antibiotic phazolicin displays a dual mode of uptake in Gram-negative bacteria

Phazolicin (PHZ) is a peptide antibiotic exhibiting narrow-spectrum activity against rhizobia closely related to its producer Rhizobium sp. Pop5. Using genetic and biochemical techniques, we here identified BacA and YejABEF as two importers of PHZ in a sensitive model strain Sinorhizobium meliloti Sm1021. BacA and YejABEF are members of SLiPT and ABC transporter families of non-specific peptide importers, respectively. The uptake of PHZ by two distinct families of transporters dramatically decreases the naturally occurring rate of resistance. Moreover, since both BacA and YejABEF are essential for the development of functional symbiosis of rhizobia with leguminous plants, the acquisition of PHZ resistance via the inactivation of transporters is further disfavoured since single bacA or yejABEF mutants are unable to propagate in root nodules. Crystal structures of the periplasmic subunit YejA from S. meliloti and Escherichia coli revealed fortuitous bound peptides, suggesting a non-specific peptide-binding mechanism that facilitates the uptake of PHZ and other antimicrobial peptides. SIGNIFICANCE Many bacteria produce antimicrobial peptides to eliminate competitors and create an exclusive niche. These peptides kill bacteria by either membrane disruption or inhibiting essential intracellular processes. The Achilles heel of the latter type of antimicrobials is their dependence on transporters to enter the susceptible bacteria since mutations in such transporters result in resistance. We describe here how the ribosome-targeting peptide phazolicin, produced by Rhizobium sp. Pop5, uses two different transporters, BacA and YejABEF, to get into the cells of the symbiotic bacterium Sinorhizobium meliloti . This dramatically reduces the probability of resistance acquisition. Both transporters need to be inactivated for phazolicin resistance acquisition. Since these transporters are also crucial in S. meliloti for its symbiotic association with host plants, their inactivation in biological settings is highly unlikely. This makes PHZ an attractive lead for the development of a biocontrol agent with potential for use in agriculture

Dual-Uptake Mode of the Antibiotic Phazolicin Prevents Resistance Acquisition by Gram-Negative Bacteria

Phazolicin (PHZ) is a peptide antibiotic exhibiting narrow-spectrum activity against rhizobia closely related to its producer, Rhizobium sp. strain Pop5. Here, we show that the frequency of spontaneous PHZ-resistant mutants in Sinorhizobium meliloti is below the detection limit. We find that PHZ can enter S. meliloti cells through two distinct promiscuous peptide transporters, BacA and YejABEF, which belong to the SLiPT (SbmA-like peptide transporter) and ABC (ATP-binding cassette) transporter families, respectively. The dual-uptake mode explains the lack of observed resistance acquisition because the simultaneous inactivation of both transporters is necessary for resistance to PHZ. Since both BacA and YejABEF are essential for the development of functional symbiosis of S. meliloti with leguminous plants, the unlikely acquisition of PHZ resistance via the inactivation of these transporters is further disfavored. A whole-genome transposon sequencing screen did not reveal additional genes that can provide strong PHZ resistance when inactivated. However, it was found that the capsular polysaccharide KPS, the novel putative envelope polysaccharide PPP (PHZ-protecting polysaccharide), as well as the peptidoglycan layer jointly contribute to the sensitivity of S. meliloti to PHZ, most likely serving as barriers that reduce the amount of PHZ transported inside the cell. IMPORTANCE Many bacteria produce antimicrobial peptides to eliminate competitors and create an exclusive niche. These peptides act either by membrane disruption or by inhibiting essential intracellular processes. The Achilles' heel of the latter type of antimicrobials is their dependence on transporters to enter susceptible cells. Transporter inactivation results in resistance. Here, we show that a rhizobial ribosome-targeting peptide, phazolicin (PHZ), uses two different transporters, BacA and YejABEF, to enter the cells of a symbiotic bacterium, Sinorhizobium meliloti. This dual-entry mode dramatically reduces the probability of the appearance of PHZ-resistant mutants. Since these transporters are also crucial for S. meliloti symbiotic associations with host plants, their inactivation in natural settings is strongly disfavored, making PHZ an attractive lead for the development of biocontrol agents for agriculture