Nature Reviews Microbiology 14, 337 (2016). doi:10.1038/nrmicro.2016.25
Authors: Suguru Okuda, David J. Sherman, Thomas J. Silhavy, Natividad Ruiz & Daniel Kahne
Gram-negative bacteria have a double-membrane cellular envelope that enables them to colonize harsh environments and prevents the entry of many clinically available antibiotics. A main component of most outer membranes is lipopolysaccharide (LPS), a glycolipid containing several fatty acyl chains and up to hundreds of
Nature Reviews Microbiology 14, 385 (2016). doi:10.1038/nrmicro.2016.30
Authors: Cherilyn Elwell, Kathleen Mirrashidi & Joanne Engel
Chlamydia spp. are important causes of human disease for which no effective vaccine exists. These obligate intracellular pathogens replicate in a specialized membrane compartment and use a large arsenal of secreted effectors to survive in the hostile intracellular environment of the host. In this
Histone post-translational modifications (HPTMs) provide signal platforms to recruit proteins or protein complexes to regulate gene expression. Therefore, the identification of these recruited partners (readers) is essential to understand the underlying regulatory mechanisms. However, it is still a major challenge to profile these partners because their interactions with HPTMs are rather weak and highly dynamic. Herein we report the development of a HPTM dual probe based on DNA-templated technology and a photo-crosslinking method for the identification of HPTM readers. By using the trimethylation of histone H3 lysine 4, we demonstrated that this HPTM dual probe can be successfully utilized for labeling and enrichment of HPTM readers, as well as for the discovery of potential HPTM partners. This study describes the development of a new chemical proteomics tool for profiling HPTM readers and can be adapted for broad biomedical applications.
Do you read me? A DNA-templated peptide probe was developed to identify the reader proteins of histone post-translational modifications. The method, based on DNA-templated chemistry and photo-crosslinking technologies, can label and enrich the reader of H3K4me3 (histone H3 lysine 4 trimethylation) in a whole cell lysate.
Antibiotics play important roles in infection treatment and prevention. However, the effectiveness of antibiotics is now threatened by the prevalence of drug-resistant bacteria. Furthermore, antibiotic abuse and residues in the environment cause serious health issues. In this study, a stimuli-responsive imprinted hydrogel was fabricated by using β-lactamase produced by bacteria for deactivating antibiotics as the template molecule. The imprinted hydrogel could initially trap β-lactamase excreted by drug-resistant bacteria, thus making bacteria sensitive to antibiotics. After the bactericidal treatment, the “imprinted sites” on the hydrogel could be reversibly abolished with a temperature stimulus, which resulted in the reactivation of β-lactamase to degrade antibiotic residues. We also present an example of the use of this antibacterial design to treat wound infection.
New hope for old drugs: β-Lactamase was used as a template molecule to fabricate a stimuli-responsive imprinted hydrogel (see picture). The hydrogel could trap β-lactamase excreted by drug-resistant bacteria, thus making the bacteria sensitive to conventional antibiotics. The thermoresponsive “binding sites” on the hydrogel could then be abolished to release β-lactamase for the degradation of antibiotic residues.
Antimicrobial peptides (AMPs) are a key component of the host's innate immune system, targeting invasive and colonizing bacteria. For successful survival and colonization of the host, bacteria have a series of mechanisms to interfere with AMP activity, and AMP resistance is intimately connected with the virulence potential of bacterial pathogens. In particular, because AMPs are considered as potential novel antimicrobial drugs, it is vital to understand bacterial AMP resistance mechanisms. This review gives a comparative overview of Gram-positive and Gram-negative bacterial strategies of resistance to various AMPs, such as repulsion or sequestration by bacterial surface structures, alteration of membrane charge or fluidity, degradation and removal by efflux pumps.
This article is part of the themed issue ‘Evolutionary ecology of arthropod antimicrobial peptides’.
A diiodo distyryl boron dipyrromethene (BODIPY) core was conjugated to two ferrocenyl quenchers through acid-labile ketal and/or thiol-cleavable disulfide linkers, of which the fluorescence and photosensitizing properties were significantly quenched through a photoinduced electron-transfer process. The two symmetrical analogues that contained either the ketal or disulfide linkers could only be activated by a single stimulus, whereas the unsymmetrical analogue was responsive to dual stimuli. Upon interaction with acid and/or dithiothreitol (DTT), these linkers were cleaved selectively. The separation of the BODIPY core and the ferrocenyl moieties restored the photoactivities of the former in phosphate buffered saline and inside the MCF-7 breast cancer cells, rendering these compounds as potential activable photosensitizers for targeted photodynamic therapy. The dual activable analogue exhibited the greatest enhancement in intracellular fluorescence intensity in both an acidic environment (pH 5) and the presence of DTT (4 mm). Its photocytotoxicity against MCF-7 cells also increased by about twofold upon preincubation with 4 mm of DTT. The activation of this compound was also demonstrated in nude mice bearing a HT29 human colorectal carcinoma. A significant increase in fluorescence intensity in the tumor was observed over 9 h after intratumoral injection.
Call to action: Three bisferrocenyl distyryl boron dipyrromethene (BODIPY) derivatives have been prepared, the photoactivities of which can be activated by acid and/or dithiothreitol (DTT) both in phosphate buffered saline and at the cellular level (see figure). The in vivo activation of the dual activable analogue has also been demonstrated.
Nature advance online publication 27 April 2016. doi:10.1038/nature17895
Authors: Mihir Pendse & Lora V. Hooper
The microorganisms that colonize pregnant mice have been shown to prime the innate immune system in newborn offspring, preparing them for life in association with microbes.
Nature Chemical Biology 12, 317 (2016). doi:10.1038/nchembio.2042
Authors: Surya A Reis, Balaram Ghosh, J Adam Hendricks, D Miklos Szantai-Kis, Lisa Törk, Kenneth N Ross, Justin Lamb, Willis Read-Button, Baixue Zheng, Hongtao Wang, Christopher Salthouse, Stephen J Haggarty & Ralph Mazitschek
Nature advance online publication 18 April 2016. doi:10.1038/nature17636
Authors: Ben C. Chung, Ellene H. Mashalidis, Tetsuya Tanino, Mijung Kim, Akira Matsuda, Jiyong Hong, Satoshi Ichikawa & Seok-Yong Lee
Antibiotic-resistant bacterial infection is a serious threat to public health. Peptidoglycan biosynthesis is a well-established target for antibiotic development. MraY (phospho-MurNAc-pentapeptide translocase) catalyses the first and an essential membrane step of peptidoglycan biosynthesis. It is considered a very promising target for the development of new antibiotics, as many naturally occurring nucleoside inhibitors with antibacterial activity target this enzyme. However, antibiotics targeting MraY have not been developed for clinical use, mainly owing to a lack of structural insight into inhibition of this enzyme. Here we present the crystal structure of MraY from Aquifex aeolicus (MraYAA) in complex with its naturally occurring inhibitor, muraymycin D2 (MD2). We show that after binding MD2, MraYAA undergoes remarkably large conformational rearrangements near the active site, which lead to the formation of a nucleoside-binding pocket and a peptide-binding site. MD2 binds the nucleoside-binding pocket like a two-pronged plug inserting into a socket. Further interactions it makes in the adjacent peptide-binding site anchor MD2 to and enhance its affinity for MraYAA. Surprisingly, MD2 does not interact with three acidic residues or the Mg2+ cofactor required for catalysis, suggesting that MD2 binds to MraYAA in a manner that overlaps with, but is distinct from, its natural substrate, UDP-MurNAc-pentapeptide. We have determined the principles of MD2 binding to MraYAA, including how it avoids the need for pyrophosphate and sugar moieties, which are essential features for substrate binding. The conformational plasticity of MraY could be the reason that it is the target of many structurally distinct inhibitors. These findings can inform the design of new inhibitors targeting MraY as well as its paralogues, WecA and TarO.
Nature Reviews Microbiology 14, 320 (2016). doi:10.1038/nrmicro.2016.34
Authors: Asher Brauner, Ofer Fridman, Orit Gefen & Nathalie Q. Balaban
Antibiotic tolerance is associated with the failure of antibiotic treatment and the relapse of many bacterial infections. However, unlike resistance, which is commonly measured using the minimum inhibitory concentration (MIC) metric, tolerance is poorly characterized, owing to the lack of a similar quantitative indicator. This
Bioorthogonal turn-on probes have been widely utilized in visualizing various biological processes. Most of the currently available bioorthogonal turn-on probes are blue or green emissive fluorophores with azide or tetrazine as functional groups. Herein, we present an alternative strategy of designing bioorthogonal turn-on probes based on red-emissive fluorogens with aggregation-induced emission characteristics (AIEgens). The probe is water soluble and non-fluorescent due to the dissipation of energy through free molecular motion of the AIEgen, but the fluorescence is immediately turned on upon click reaction with azide-functionalized glycans on cancer cell surface. The fluorescence turn-on is ascribed to the restriction of molecular motion of AIEgen, which populates the radiative decay channel. Moreover, the AIEgen can generate reactive oxygen species (ROS) upon visible light (λ=400–700 nm) irradiation, demonstrating its dual role as an imaging and phototherapeutic agent.
Fast and specific: A bioorthogonal turn-on probe based on a red-emissive fluorogen with aggregation-induced emission characteristics (AIEgen) was developed for cancer cell imaging and photodynamic ablation. The fluorescence is immediately turned on upon click reaction with azide-functionalized glycans on a cancer cell surface.
