17 research outputs found
Flipping the switch: dynamic modulation of membrane transporter activity in bacteria
The controlled entry and expulsion of small molecules across the bacterial cytoplasmic membrane is essential for efficient cell growth and cellular homeostasis. While much is known about the transcriptional regulation of genes encoding transporters, less is understood about how transporter activity is modulated once the protein is functional in the membrane, a potentially more rapid and dynamic level of control. In this review, we bring together literature from the bacterial transport community exemplifying the extensive and diverse mechanisms that have evolved to rapidly modulate transporter function, predominantly by switching activity off. This includes small molecule feedback, inhibition by interaction with small peptides, regulation through binding larger signal transduction proteins and, finally, the emerging area of controlled proteolysis. Many of these examples have been discovered in the context of metal transport, which has to finely balance active accumulation of elements that are essential for growth but can also quickly become toxic if intracellular homeostasis is not tightly controlled. Consistent with this, these transporters appear to be regulated at multiple levels. Finally, we find common regulatory themes, most often through the fusion of additional regulatory domains to transporters, which suggest the potential for even more widespread regulation of transporter activity in biology
The impact of surgical delay on resectability of colorectal cancer: An international prospective cohort study
AIM: The SARS-CoV-2 pandemic has provided a unique opportunity to explore the impact of surgical delays on cancer resectability. This study aimed to compare resectability for colorectal cancer patients undergoing delayed versus non-delayed surgery. METHODS: This was an international prospective cohort study of consecutive colorectal cancer patients with a decision for curative surgery (January-April 2020). Surgical delay was defined as an operation taking place more than 4 weeks after treatment decision, in a patient who did not receive neoadjuvant therapy. A subgroup analysis explored the effects of delay in elective patients only. The impact of longer delays was explored in a sensitivity analysis. The primary outcome was complete resection, defined as curative resection with an R0 margin. RESULTS: Overall, 5453 patients from 304 hospitals in 47 countries were included, of whom 6.6% (358/5453) did not receive their planned operation. Of the 4304 operated patients without neoadjuvant therapy, 40.5% (1744/4304) were delayed beyond 4 weeks. Delayed patients were more likely to be older, men, more comorbid, have higher body mass index and have rectal cancer and early stage disease. Delayed patients had higher unadjusted rates of complete resection (93.7% vs. 91.9%, P = 0.032) and lower rates of emergency surgery (4.5% vs. 22.5%, P < 0.001). After adjustment, delay was not associated with a lower rate of complete resection (OR 1.18, 95% CI 0.90-1.55, P = 0.224), which was consistent in elective patients only (OR 0.94, 95% CI 0.69-1.27, P = 0.672). Longer delays were not associated with poorer outcomes. CONCLUSION: One in 15 colorectal cancer patients did not receive their planned operation during the first wave of COVID-19. Surgical delay did not appear to compromise resectability, raising the hypothesis that any reduction in long-term survival attributable to delays is likely to be due to micro-metastatic disease
Fluorescence-based thermal shift data on multidrug regulator AcrR from Salmonella enterica subsp. entrica serovar Typhimurium str. LT2
The fluorescence-based thermal shift (FTS) data presented here include Table S1 and Fig. S1, and are supplemental to our original research article describing detailed structural, FTS, and fluorescence polarization analyses of the Salmonella enterica subsp. entrica serovar Typhimurium str. LT2 multidrug transcriptional regulator AcrR (StAcrR) (doi:10.1016/j.jsb.2016.01.008) (Manjasetty et al., 2015 [1]). Table S1 contains chemical formulas, a Chemical Abstracts Service (CAS) Registry Number (CAS no.), FTS rank (a ligand with the highest rank) has the largest difference in the melting temperature (ΔTm), and uses as drug molecules against various pathological conditions of sixteen small-molecule ligands that increase thermal stability of StAcrR. Thermal stability of human enolase 1, a negative control protein, was not affected in the presence of various concentrations of the top six StAcrR binders (Fig. S1). Keywords: Fluorescence-based thermal shift analysis, Infectious diseases, Transcriptional regulator, TetR, AcrR, Salmonella enterica, High-throughout screenin
Structure-Guided, Single-Point Modifications in the Phosphinic Dipeptide Structure Yield Highly Potent and Selective Inhibitors of Neutral Aminopeptidases
Seven crystal structures of alanyl
aminopeptidase from <i>Neisseria meningitides</i> (the etiological
agent of meningitis, <i>Nm</i>APN) complexed with organophosphorus
compounds were resolved
to determine the optimal inhibitor–enzyme interactions. The
enantiomeric phosphonic acid analogs of Leu and hPhe, which correspond
to the P1 amino acid residues of well-processed substrates, were used
to assess the impact of the absolute configuration and the stereospecific
hydrogen bond network formed between the aminophosphonate polar head
and the active site residues on the binding affinity. For the hPhe
analog, an imperfect stereochemical complementarity could be overcome
by incorporating an appropriate P1 side chain. The constitution of
P1′-extended structures was rationally designed and the lead,
phosphinic dipeptide hPhePψ[CH<sub>2</sub>]Phe, was modified
in a single position. Introducing a heteroatom/heteroatom-based fragment
to either the P1 or P1′ residue required new synthetic pathways.
The compounds in the refined structure were low nanomolar and subnanomolar
inhibitors of <i>N. meningitides</i>, porcine and human
APNs, and the reference leucine aminopeptidase (LAP). The unnatural
phosphinic dipeptide analogs exhibited a high affinity for monozinc
APNs associated with a reasonable selectivity versus dizinc LAP. Another
set of crystal structures containing the <i>Nm</i>APN dipeptide
ligand were used to verify and to confirm the predicted binding modes;
furthermore, novel contacts, which were promising for inhibitor development,
were identified, including a π–π stacking interaction
between a pyridine ring and Tyr372
Characterization of Member of DUF1888 Protein Family, Self-cleaving and Self-assembling Endopeptidase
<i>Bacillus anthracis</i> Inosine 5′-Monophosphate Dehydrogenase in Action: The First Bacterial Series of Structures of Phosphate Ion‑, Substrate‑, and Product-Bound Complexes
Inosine 5′-monophosphate dehydrogenase (IMPDH)
catalyzes
the first unique step of the GMP branch of the purine nucleotide biosynthetic
pathway. This enzyme is found in organisms of all three kingdoms.
IMPDH inhibitors have broad clinical applications in cancer treatment,
as antiviral drugs and as immunosuppressants, and have also displayed
antibiotic activity. We have determined three crystal structures of <i>Bacillus anthracis</i> IMPDH, in a phosphate ion-bound (termed
“apo”) form and in complex with its substrate, inosine
5′-monophosphate (IMP), and product, xanthosine 5′-monophosphate
(XMP). This is the first example of a bacterial IMPDH in more than
one state from the same organism. Furthermore, for the first time
for a prokaryotic enzyme, the entire active site flap, containing
the conserved Arg-Tyr dyad, is clearly visible in the structure of
the apoenzyme. Kinetic parameters for the enzymatic reaction were
also determined, and the inhibitory effect of XMP and mycophenolic
acid (MPA) has been studied. In addition, the inhibitory potential
of two known <i>Cryptosporidium parvum</i> IMPDH inhibitors
was examined for the <i>B. anthracis</i> enzyme and compared
with those of three bacterial IMPDHs from <i>Campylobacter jejuni</i>, <i>Clostridium perfringens</i>, and <i>Vibrio cholerae</i>. The structures contribute to the characterization of the active
site and design of inhibitors that specifically target <i>B.
anthracis</i> and other microbial IMPDH enzymes
Interaction of J-Protein Co-Chaperone Jac1 with Fe–S Scaffold Isu Is Indispensable In Vivo and Conserved in Evolution
Comparison of nasal and bronchial epithelial cells obtained from patients with COPD
For in vitro studies of airway pathophysiology, primary epithelial cells have many advantages over immortalised cell lines. Nasal epithelial cells are easier to obtain than bronchial epithelial cells and can be used as an alternative for in vitro studies. Our objective was to compare nasal and bronchial epithelial cells from subjects with COPD to establish if these cells respond similarly to pro-inflammatory stimuli. Cell cultures from paired nasal and bronchial brushings (21 subjects) were incubated with cigarette smoke extract (CSE) prior to stimulation with Pseudomonas aeruginosa lipopolysaccharide. IL-6 and IL-8 were measured by ELISA and Toll-like receptor 4 (TLR-4) message and expression by RT-PCR and FACS respectively. IL-8 release correlated significantly between the two cell types. IL-6 secretion was significantly less from bronchial compared to nasal epithelial cells and secreted concentrations did not correlate. A 4 h CSE incubation was immunosuppressive for both nasal and bronchial cells, however prolonged incubation for 24 h was pro-inflammatory solely for the nasal cells. CSE reduced TLR-4 expression in bronchial cells only after 24 h, and was without effect on mRNA expression. In subjects with COPD, nasal epithelial cells cannot substitute for in vitro bronchial epithelial cells in airway inflammation studies