Cyclic Nucleotides
Enrique Pimentel in Handbook of Growth Factors, 2017
cAMP is present in both animals and plants and is involved in the regulation of gene expression.38 It functions as an important regulator of transcription in prokaryotes, acting through its binding to a specific receptor protein, the catabolite-gene activator protein (CAP). The cAMP-CAP complex binds to specific bacterial DNA sequences and thus can enhance the rate of transcription of several operons. As for bacteria, cAMP is involved in the regulation of gene expression in eukaryotes, where it may act as either an activator or an inhibitor of transcription.39,40 Expression of cAMP-responsive genes in higher eukaryotes is controlled by proteins that form complexes with cAMP and then display sequence-specific DNA-binding properties. cAMP response elements (CREs) are contained in the promoters of eukaryotic cAMP-inducible genes, and the CREs are recognized by CRE-binding proteins.41,42 Nuclear extracts from rat liver contain a cAMP-dependent factor capable of specific binding to a synthetic fragment of 46 bp whose sequence corresponds to that of the 5’ flanking region of a gene known to contain the element that confers regulation of transcription of this gene by cAMP.43 The 5’-flanking region of the rat corticotropin-releasing hormone (CRH) gene contains a CRE that is localized to the DNA sequence from -238 to -180 bp relative to the putative CRH mRNA cap site.44 The CRE of the rat CRH gene is conserved at 58/59 bases in the human genome, suggesting an important role for this CRE in the regulation of gene expression.
Physiology and Growth
Paul Pumpens in Single-Stranded RNA Phages, 2020
Brief mention should be made of the nice and popular hypothesis based on the discovery of a ψr factor. ψr factor was found by Travers et al. (1970a,b) and postulated as a common activity that participated in the synthesis of both rRNA and phage RNA, in the latter case as a hypothetical component of the phage Qβ replicase. Chapter 13 will describe the further development of this hypothesis to the clear observation, but in 1970 it seemed clear enough to explain the competitive character of the rRNA and phage RNA synthesis. Travers et al. (1970b) tried to connect the ψr factor with the CAP, or catabolite gene activator protein, regulated by cyclic AMP, or cyclic 3′: 5′-adenosine monophosphate (Zubay et al. 1970). However, the first experimental response to the ψr hypothesis indicated that the decreased availability of ψr was probably not the cause of the reduced host RNA synthesis which followed infection with the phage R23 (Hunt and Watanabe 1971).
Genetically Engineered Oncolytic Salmonella typhimurium
Ananda M. Chakrabarty, Arsénio M. Fialho in Microbial Infections and Cancer Therapy, 2019
Gene expression under the control of a pBAD promoter is tightly regulated by a nontoxic sugar, l-arabinose. The pBAD promoter originates from the E. coli arabinose operon. The pC promoter, which constitutively controls the transcription of araC in the opposite direction, is adjacent to the pBAD promoter. Constitutively expressed AraC positively and negatively regulates gene transcription by binding to the pBAD promoter. In the absence of l-arabinose, AraC dimerizes the O2 and Ix operator sites, forming a DNA loop. This looping prevents transcription of pBAD and pC by inhibiting the binding of cyclic AMP receptor protein (CAP) and RNA polymerase. In the presence of l-arabinose, arabinose bound to AraC dimerizes the Ix and I2 operators, allowing CAP and RNA polymerase to bind to linear DNA, activating the transcription of the pBAD and pC promoters. The pBAD promoter has been found to be an excellent promoter, with gene expression tightly regulated by l-arabinose, thus allowing the precise expression of target genes in vivo by remote control [6, 17, 29].
Molecules involved in motility regulation in Escherichia coli cells: a review
Published in Biofouling, 2020
Fazlurrahman Khan, Nazia Tabassum, Dung Thuy Nguyen Pham, Sandra Folarin Oloketuyi, Young-Mog Kim
The roles of cyclic AMP-catabolite activator protein complex (CAP) and histone-like nucleoid-structuring (H-NS) protein are also important in the regulation of flagellum biosynthesis in E. coli and the expression of several genes responding to changes in environmental conditions such as pH, temperature, and osmolarity (Soutourina et al. 1999). The H-NS regulates the motility by inhibiting the activity of several molecules such as c-di-GMP, CasgD, and sigma factors (σS and σF) (Kim and Blair 2015). Similarly, the cAMP-CAP complex activates the expression of flagellar genes by binding to the promoter of the flhDC (Soutourina et al. 1999). Homologs of cAMP-CAP and a conserved binding site for cAMP-CAP in the promoter region of flhDC have been identified in several enterobacteria species as well (Soutourina and Bertin 2003). Hence, the activation of flhDC expression in other enterobacteria is presumed to be conserved and occur in similar ways to those reported previously for E. coli (Soutourina et al. 1999).
Systematic review and meta-analysis of the safety of erythromycin compared to clarithromycin in adults and adolescents with pneumonia
Published in Journal of Chemotherapy, 2020
Khalid Eljaaly, Ahmed Botaish, Fawaz Bahobail, Mohamed Almehmadi, Ziyad Assabban, Abrar K. Thabit, Basem Alraddadi, Ahmed Aljabri, Nasser Alqahtani, Mohammed A. Aseeri, Almoutaz Hashim, Antoni Torres
Community-acquired pneumonia (CAP) is a serious lung infection and among infectious diseases one of leading causes of morbidity and mortality in the world.1 In the United States, it is considered the 8th leading cause of death. Moreover, it is the most common cause of death from infection in developing countries.2 Macrolides, namely azithromycin, clarithromycin, and erythromycin, are commonly used to treat several bacterial respiratory tract infections, particularly CAP.3–5 This is partially attributed to their coverage of atypical bacteria, which are commonly implicated in CAP.6 Clarithromycin has a similar spectrum of activity as the prototypical macrolide erythromycin, covering atypical bacteria as well as some Gram-positive and Gram-negative bacteria; however, its activity extends against Streptococcus pneumonia and Haemophilus influenzae.7 The emergence of macrolide-resistant Streptococci, such as S. pneumoniae and S. pyogenes, is concerning and most resistance is caused by erm and mef genes, some of which can be inducible.8,9 Clarithromycin also carries the advantages of being more stable in gastric acid and achieves better bioavailability when taken orally. It also has a longer half-life, which provides lower frequency of administration (q12h vs. q6h with erythromycin), potentially improving patient adherence.7,10
Biochemical and immunocytochemical characterization of coronins in platelets
Published in Platelets, 2020
David R. J. Riley, Jawad S. Khalil, Khalid M. Naseem, Francisco Rivero
Platelets are anucleate fragments of megakaryocytes that play pivotal roles in hemostasis, thrombosis, wound healing and immunological processes. Platelets display a remarkable morphological plasticity. While in circulation they have a characteristic discoid shape, but are capable of undergoing profound changes upon adhesion to damaged blood vessel walls, transitioning to a spherical shape that extends filopodia and lamellipodia as the cell spreads and flattens [1]. This process is accompanied by secretion of granules and activation of integrins that support and consolidate the formation of a platelet aggregate. Remodeling of the cytoskeleton, formed by a network of actin filaments and a marginal ring of microtubules and associated proteins constitutes a crucial aspect of platelet function and is the result of multiple exquisitely integrated signaling cascades [2]. A plethora of proteins with various biochemical activities is responsible for the dynamics of actin remodeling during platelet activation, including actin nucleators like formins and the Arp2/3 complex and their regulators (WAVE, WASP), monomeric actin-binding proteins like profilin, β-thymosin and the cyclase-associated protein (CAP) and others like gelsolin, cofilin, and coronins [3–5].
Related Knowledge Centers
- Activator
- Allosteric Regulation
- Cooperativity
- Cyclic Adenosine Monophosphate
- Ligand
- Protein Dimer
- Camp Receptor Protein
- N-Terminus
- DNA-Binding Domain
- C-Terminus