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The Single-Stranded DNA Binding Protein of Bacteriophage T4
Published in James F. Kane, Multifunctional Proteins: Catalytic/Structural and Regulatory, 2019
Daniel H. Doherty, Peter Gauss, Larry Gold
Structural domains of proteins are portions of a polypeptide that can act autonomously; that is, they independently possess some property of an individual protein.27 For example, the cl repressor protein of bacteriophage lambda has been shown to contain two domains.28 Partial proteolysis of cI protein yields two fragments, one containing the aminoterminus, the other containing the carboxyterminus. Each of these fragments independently possesses one function of the mature protein. The native protein binds to specific nucleotide sequences in λ DNA (the operators) and also forms dimers. The aminoterminal fragment binds operator DNA, but does not dimerize.29 Conversely, the carboxyterminal fragment forms dimers but does not bind the operator sequences.28
REGULATORY MECHANISMS
Published in David M. Gibson, Robert A. Harris, Metabolic Regulation in Mammals, 2001
David M. Gibson, Robert A. Harris
The receptor with bound ligand is the active conformation that initiates the signal cascade leading to glvcogcnolvsis. It moves against a neighboring tripartite uG,-protein complex" ((ITI* (ìDI* binding protein) and drives a change in the conformation ol the (il I* CIDI1 binding coni|>oncnt Iroin an inactive to an ait i ve state. (1 ripartite means that this type ol Ci protein svstcm consists ol three subunits. These are
Inhibition of Shiga toxin-converting bacteriophage development by novel antioxidant compounds
Published in Journal of Enzyme Inhibition and Medicinal Chemistry, 2018
Sylwia Bloch, Bożena Nejman-Faleńczyk, Karolina Pierzynowska, Ewa Piotrowska, Alicja Węgrzyn, Christelle Marminon, Zouhair Bouaziz, Pascal Nebois, Joachim Jose, Marc Le Borgne, Luciano Saso, Grzegorz Węgrzyn
It was previously proposed that OxyR may be responsible for the lambdoid prophage maintenance under conditions of the oxidative stress8. Other studies indicated that under such conditions, activated OxyR is able to compete effectively with the cI protein (the main repressor of phage lytic development) for the binding to the oR3 operator of the pM-pR promoter region30. These results allowed to suggest that OxyR might enhance repression of pR (the major promoter for expression of genes of phage lytic lifecycle) and enhance activation, and at the same time also downregulate repression, of the transcription of the cI gene from the pM promoter. This would lead to higher (relative to normal growth conditions) activity of pM, increased production of cI repressor and lower efficiency of prophage induction under the oxidative stress.
Bacteriophages for ESKAPE: role in pathogenicity and measures of control
Published in Expert Review of Anti-infective Therapy, 2021
Amrita Patil, Rajashri Banerji, Poonam Kanojiya, Santosh Koratkar, Sunil Saroj
A strong association has been reported between the expression of lysogeny module, lytic module, and virulence factor, which influence the expression of pathogenicity genes during bacteriophage induction. The lysogeny module encodes integrase (Int, CI) and regulator proteins (Cro). The transition between the lysogenic and lytic life cycle is determined by the expression of int, CI, and Cro proteins. The Int protein assists in the integration of the phage genome in the bacterial chromosome. The expression of CI protein maintains a lysogenic state. However, the expression of Cro triggers the lytic cycle of the phage. Prophage with int gene has been recently found in the epidemic methicillin-resistant Staphylococcus aureus strain. Also, the two-component regulatory system (quorum-sensing system) is found to be involved in the expression of phage-encoded virulence factors such as eta, pvl, scn, and chp. It indicates a close association between the phage life cycle and bacterial virulence. It has been also observed that phage inducing conditions such as exposure to UV, reactive oxygen species, antibiotics, and change in nutrients, pH, temperature increases transcription of the virulence factors that are present in proximity to the lysis module of the phage genome. The methicillin-resistant S. aureus isolated from the skin or soft tissue infection, and necrotizing pneumonia, indicated the role of the lukSf comprising bacteriophages in the pathogenicity of S. aureus. Generally, most of the bacteriophages consist of one virulence factor. However, certain bacteriophages like phiSa3 and phiN315 code for almost five virulence factors. S. aureus bacteriophages Sa3int codes for immune evasion cluster and immune-modulatory proteins such as Chips, Sak, Sea, and Scin that may support the colonization of the strain regardless of the innate immune response [118,119]. Moreover, S. aureus bacteriophages mediate the transfer of SaPIs encoding for toxins and contribute to enhanced pathogenicity of the recipient bacterial cell. The bacteriophage dynamics in the form of transfer of the bacteriophage, duplication, and stable extrachromosomal integration generate heterogeneity within the infecting bacterial population, by regulating the virulence factors and thus increase the pathogenic potential of the whole bacterial consortium [119].