China
Africa
Explore chapters and articles related to this topic
Techniques for Isolation and Evaluation
Published in Shojiro Inoué, Biology of Sleep Substances, 2020
After chromatography on SP-Sephadex® (steps 6 and 7), several adjacent eluates were found to be active. Each was taken separately through the remainder of the purification program. Acid hydrolysis of the final purified fractions released glutamic acid (Glu), alanine (Ala), diaminopimelic acid (Dap), and glycine. The apparent molar ratios of Glu/Ala/Dap were 2:2:1. Since Dap is a constituent of bacterial peptideglycans, Krueger et al.48 supposed that their purified fractions might contain amino sugars. The sample was then subjected to mild acid hydrolysis, followed by amino acid analysis. Thus, it was determined that muramic acid was equimolar with Dap, whereas glucosamine was equimolar with glycine. Hence, urinary Factor S was proven to be a small glycopeptide.
Phagocytosis By Human Neutrophils
Published in Hans H. Gadebusch, Phagocytes and Cellular Immunity, 2020
An alternative M0P-H2O2-C1 bactericidal mechanism has been suggested by Selvaraj et al.296 These workers grew a mutant of E. coli that required exogenous diaminopimelic acid on the radiolabeled compound. When the radioactive bacteria were later incubated with H2O2, Cl", and MPO,,4CO2 was liberated. The amount of 14CO2 released was greater than could be accounted for simply by decarboxylation of the free carboxy terminus, and the authors suggested that this bactericidal system was operating by the actual cleavage of peptide bonds in the bacterial protein (as illustrated in Figure 7). This hypothesis could be easily tested by growing normal bacteria on amino acids labeled with,4C in the carboxyl group and measuring the I4CO2 released during incubation with MP0-H2O2-C1; such experiments have not been reported to my knowledge, and this mechanism must be regarded as tentative.
Physiology and Growth
Published in Paul Pumpens, Single-Stranded RNA Phages, 2020
An unexpected interference of the phage Qβ infection with the E. coli host cell functions, which led to alteration of the host character, was described by Miyake et al. (1966): the number of colonies formed by lac− host on minimal lactose agar medium increased 15 times when the host was plated after Qβ infection. This effect was explained by the concomitant liberation of β-galactosidase accumulated in constitutive cells together with the liberation of phage and the increase of the extracellular β-galactosidase. Furthermore, the Qβ infection caused a codon-specific change in the function of tRNA: preparations of the latter from infected cells showed a markedly decreased ability to support translation of polycytidylic acid into polypeptide, as compared to tRNA from uninfected cells, whereas polyuridylic acid−directed phenylalanine incorporation was not influenced (Hung and Overby 1968). This phenomenon was explained by 2−3 times decrease in ribosomal binding of the prolyl-tRNA. Another new function of the Qβ infection consisted in the inhibition of bacterial cell wall mucopeptide synthesis: incorporation of 3H-diaminopimelic acid into the mucopeptide layer of the cell wall was markedly decreased starting at about the midpoint of the phage replication cycle (Ozaki and Valentine 1973).
Increased inflammatory responsiveness of peripheral blood mononuclear cells (PBMCs) to in vitro NOD2 ligand stimulation in patients with ankylosing spondylitis
Published in Immunopharmacology and Immunotoxicology, 2018
Negar Vanaki, Taghi Golmohammadi, Ahmadreza Jamshidi, Maryam Akhtari, Mahdi Vojdanian, Shayan Mostafaei, Shiva Poursani, Nooshin Ahmadzadeh, Mahdi Mahmoudi
The innate immune system provides the first and immediate response to foreign agents through pattern recognition receptors (PRRs). Members of the PRR family are able to recognize conserved molecular patterns in pathogens or signals released from stressed or damaged cells [10]. The nucleotide-binding oligomerization domain-containing protein (NOD)1 and NOD2 are two cytosolic members in this family that recognize specific peptidoglycan (PGN) structures in bacterial cell walls. NOD1 can sense meso-diaminopimelic acid (DAP) in Gram negative bacteria. However, NOD2 functions as the general sensor of bacteria by recognizing muramyl dipeptide (MDP). Following interaction with ligands, both the receptors recruit receptor-interacting protein kinase 2 (RIPK2) to initiate the transcription of proinflammatory cytokines [11,12].
The use of Drosophila melanogaster as a model organism to study immune-nanotoxicity
Published in Nanotoxicology, 2019
Cheng Teng Ng, Liya E Yu, Choon Nam Ong, Boon Huat Bay, Gyeong Hun Baeg
The immune deficiency (Imd) pathway is also important for the microbial-sensing system in Drosophila; similar to the tumor necrosis factor (TNF) pathway and the TIR domain-containing adaptor-inducing IFN-β (TRIF)-dependent TLR pathway (Figure 4). Both Toll and Imd pathways are active in the fat body, controlling the systemic production of AMPs. Notably, Drosophila has a distinct pathway, comprising Death related ced-3/Nedd2-like (Dredd; similar to human caspase-8), dIKK-γ, dIKK-β and Relish (Rel) that responds to gram-negative bacterial infection, and the pathway is separated from fungal and gram-positive bacterial infection (Janeway and Medzhitov, 2002; Hedengren et al., 1999; Rutschmann et al., 2000b; Leulier et al., 2000). In support of this, loss-of-function mutations in these genes resulted in an increased susceptibility of Drosophila to gram-negative bacterial infection. Relish belongs to the Drosophila homolog of the Rel/NF-κB family members, p100 and p105 in mammalian system (Mukherjee et al., 2014); while dIKK-γ and dIKK-β are the Drosophila homologs of IKK-γ (also known as NEMO) and IKK-β. In human cells, IKK-β and NEMO act as an essential regulator in NF-κB activation (Yamaoka et al., 1998; Janeway and Medzhitov, 2002). The Imd pathway is induced when diaminopimelic acid (DAP)-type peptidoglycan (produced by Gram-negative bacteria and Bacillus species) is recognized by surface-bound PGRP-LC and cytosolic PGRP-LE. This then triggers the NF-κB signaling pathway and induces the expression of effectors such as AMPs (Kaneko et al., 2006; Lim et al., 2006; Chang et al., 2006).
Synthesis, molecular docking, binding free energy calculation and molecular dynamics simulation studies of benzothiazol-2-ylcarbamodithioates as Staphylococcus aureus MurD inhibitors
Published in Journal of Receptors and Signal Transduction, 2019
Srikanth Jupudi, Mohammed Afzal Azam, Ashish Wadhwani
Infections caused by methicillin-resistant Staphylococcus aureus (MRSA) are a leading cause of mortality and morbidity in humans around the world. It has emerged as a major public health threat and responsible for patient morbidity and mortality [1,2]. The alarming rise of S. aureus resistance to most of the antibiotics [3] has rendered the discovery of new antibacterial agents with potential novel mechanisms of action is critically important. Peptidoglycan (PG), part of the cell envelope of S. aureus, is essential to maintain the structural integrity of the cell wall. Its biosynthesis in bacteria is well understood and considered to be a potential target for the development of novel antibacterial drugs [4,5]. The ATP-dependent bacterial Mur ligases (MurC-F) catalyze the sequential addition of L-alanine, D-glutamic acid (D-Glu) and meso-2,6-diaminopimelic acid (meso-DAP) in Gram-negative or L-lysine in Gram-positive bacteria, and D-alanine-D-alanine dipeptide to UDP-N-acetyl muramic acid (UDP-MurNAc), to form UDP-MurNAc pentapeptide [6,7]. All Mur ligases share a common three-domain topology and most likely they operate by similar mechanisms of enzyme catalysis [8]. The multiple amino acid sequence alignment of Mur ligase orthologues and paralogues revealed relatively low overall homologies. However, the catalytic pocket binding residues are well conserved throughout the family [9–11]. Further, the cloned S. aureus MurD exhibited high percentage similarity to MurD proteins from Escherichia coli (54%), Haemophilus influenzae (55%), Bacillus subtilis (65%) and Streptococcus pyogenes (66%) [12].