Beneficial Lactic Acid Bacteria
K. Balamurugan, U. Prithika in Pocket Guide to Bacterial Infections, 2019
The proteolytic system of LAB provides amino acids essential for bacterial growth by protein conversion. It is also engaged in generation of flavor compounds, accounting for the development of organoleptic properties of fermented food (Liu et al. 2010). Two major pathways convert amino acids to flavor compounds: elimination reactions catalyzed by lyases and pathways initiated by aminotransferases. Lyases take part in the production of methanethiol from methionine, while aminotransferases convert amino acids to corresponding α-keto acids. The α-keto acids are key intermediates in aroma generation and can be further transformed into other compounds: α-hydroxyacids, acetyl-CoA derivatives, and aldehydes while the latter turn into alcohols and carboxylic acids (Steele et al. 2013). The proteolytic system of LAB contains cell wall–bound proteinase degrading milk proteins into oligopeptides, peptide transporters transferring peptides into the cell, and various intracellular peptidases breaking down the peptides into shorter peptides and amino acids (Liu et al. 2010).
Chloramphenicol
Thomas T. Yoshikawa, Shobita Rajagopalan in Antibiotic Therapy for Geriatric Patients, 2005
Chloramphenicol enters the cell by an energy-dependent process (3). Inside the bacterial cell, it inhibits protein synthesis by binding to the larger 50S subunit of the 70S ribosome. Mammalian cells contain primarily 80S ribosomes that are supposedly unaffected by chloramphenicol. However, mammalian mitochondria do contain 70S particles. The effect of chloramphenicol on these mitochondrial 70S ribosomes has been suggested as a cause for the dose-related bone marrow suppression of chloramphenicol but not the idiosyncratic aplastic anemia (4). The block in bacterial protein synthesis produces a static effect against susceptible microorganisms. However, chloramphenicol is bactericidal against some pathogens such as Haemophilus influenzae, Streptococcus pneumoniae, and Neisseria meningitides (5,6).
Selective Gene De-Repression By De-Repressor RNA
M. Gerald, M.D. Kolodny in Eukaryotic Gene Regulation, 2018
Gene regulation in lower organisms, especially bacteria, is mediated largely by protein molecules acting as repressors or inducers of gene activity.16 In these prokaryote organisms, criteria of fitness involve maximum growth when the environment permits it and minimum growth when the environment demands it. By contrast, in higher organisms the internal environment of the organism is more stable, and criteria of fitness involve restraint of growth in a balanced manner and specialization of function of each cell. Although some protein mechanisms for gene regulation are retained in higher organisms, it is not surprising that the special needs for balanced growth and specialized function in higher organisms should also utilize the higher degree of gene selectivity offerred by RNA molecules.
Platform development for expression and purification of stable isotope labeled monoclonal antibodies in Escherichia coli
Published in mAbs, 2018
Prasad T. Reddy, Robert G. Brinson, J. Todd Hoopes, Colleen McClung, Na Ke, Lila Kashi, Mehmet Berkmen, Zvi Kelman
Most protein translation in E. coli initiates by binding of the ribosome at the ribosome binding site (RBS) on the mRNA. The RBS, also referred to as the Shine-Dalgarno (SD) sequence, is located 5–10 bases upstream of the start codon. This is predominantly ATG and accounts for about 85% of initiation sites in bacteria. Other, less frequent, initiation sites are also used, including GTG and TTG. However, not all bacterial genes contain a RBS, and other mechanisms initiate translation of those genes.25 Scanning the RNA sequence upstream of the putative internal GTG initiation site did not identify any clear SD sequence. To confirm that the truncation product observed (Figure 1, lane 1) is the result of internal translation initiation and not due to another reason, the GTG codon was replaced with GTT. While both GTG and GTT encode for Val, only GTG is known to function as an initiation codon. As shown in Figure 4, the protein purified on Protein-A column from cells expressing the eNISTmAb in which the GTG codon was replaced by GTT resulted in substantial reduction in the truncated heavy chain (Figure 4, compare lane 2 to lane 1).
Noradrenergic gating of long-lasting synaptic potentiation in the hippocampus: from neurobiology to translational biomedicine
Published in Journal of Neurogenetics, 2018
Peter V. Nguyen, Jennifer N. Gelinas
One important process where various signals and transmitters can act to regulate protein synthesis is at the level of translation initiation, a rate-limiting step in translation of many species of mRNA. Here, different protein kinases act to phosphorylate eukaryotic initiation factors (eIFs) involved in the assembly of translation initiation complexes that promote mRNA binding to ribosomal proteins (Costa-Mattioli et al., 2009). For example, two key protein kinases, extracellular signal-regulated protein kinase (ERK) and mammalian target of rapamycin (mTOR), play an important role in formation of the eukaryotic initiation factor 4F (eIF4F) complex (Gelinas et al., 2007; Kelleher, Govindarajan, & Tonegawa, 2004; Klann, Antion, Banko, & Hou, 2004; Tsokas, Ma, Iyengar, Landau, & Blitzer, 2007). The eIF4F initiation complex is assembled from the initiation factors eIF4A, 4E, and 4 G (Figure 1). In the basal state, formation of eIF4F is restrained by binding of eIF4E to the inhibitory protein, 4E-binding protein (4E-BP) (Banko et al., 2005). Phosphorylation of 4E-BP by mTOR triggers the release of eIF4E, which can then associate with eIF4G and form the eIF4F complex (Figure 1). In addition, ERK phosphorylates and activates the protein kinase, Mnk1 (MAPK signal-integrating kinase-1), which in turn phosphorylates 4E to further enhance translation.
Potential utility of nano-based treatment approaches to address the risk of Helicobacter pylori
Published in Expert Review of Anti-infective Therapy, 2022
Sohaib Khan, Mohamed Sharaf, Ishfaq Ahmed, Tehsin Ullah Khan, Samah Shabana, Muhammad Arif, Syed Shabi Ul Hassan Kazmi, Chenguang Liu
In addition, Sharaf and coworkers reported that a combination of nanostructured lipid carriers with magnetic NPs, loaded with two antibiotics (AMX and CLR) for drug delivery have shown a double therapy for H. pylori. A decline in the side effects of antimicrobial drugs on normal cells, overcoming antibiotic resistance and the long-term sustainable release of both drugs by different mechanisms are as follows: NLCs adhesion caused destabilization and disruption of the outer membrane.The Fe3O4 NPs released metal ions inside the bacterial cell and generated ROS, including free radicals occurring damage and killing of the bacteria.Activation of the autolytic enzymes in the bacterial cell wall by AMX, which leads to cell wall lysis, and thus, the destruction of the bacterial cell.The action of CLR with 23S rRNA is responsible for the synthesis of protein structure. This binding interferes with protein elongation and effectively blocks the protein structure synthesis in the bacterial cell, and thus inhibits the growth of bacterial cells [45].