scholarly journals Portal protein functions akin to a DNA-sensor that couples genome-packaging to icosahedral capsid maturation

2017 ◽  
Vol 8 (1) ◽  
Author(s):  
Ravi K. Lokareddy ◽  
Rajeshwer S. Sankhala ◽  
Ankoor Roy ◽  
Pavel V. Afonine ◽  
Tina Motwani ◽  
...  
Keyword(s):  
Dna Sensor ◽  
Genome Packaging ◽  
Portal Protein ◽  
Protein Functions ◽  
Capsid Maturation ◽  
Icosahedral Capsid

scholarly journals Cryo-EM analysis of a viral portal protein in situ reveals a switch in the DNA tunnel

2019 ◽  
Author(s):  
Oliver W. Bayfield ◽  
Alasdair C. Steven ◽  
Alfred A. Antson
Keyword(s):  
Surface Properties ◽  
Dynamic Processes ◽  
Viral Capsid ◽  
Capsid Assembly ◽  
Genome Packaging ◽  
Dna Viruses ◽  
Portal Protein ◽  
Double Stranded Dna ◽  
Protein Functions

The portal protein is a key component of many double-stranded DNA viruses, governing capsid assembly and genome packaging. Twelve subunits of the portal protein form a ring with a central tunnel, through which DNA is translocated into the capsid. It is unknown how the portal protein functions as a gatekeeper, preventing DNA slippage, whilst allowing its passage into the capsid through its central tunnel, and how these processes can be controlled by capsid and motor proteins. A cryo-EM structure of a portal protein, determined in situ for immature capsids of thermostable bacteriophage P23-45, suggests how domain adjustments can be coupled with a switching of properties of the DNA tunnel. Of particular note is an inversion of the conformation of portal loops which define the tunnel’s constriction, accompanied by a switching of surface properties from hydrophobic to hydrophilic. These observations indicate how translocation of DNA into the viral capsid can be modulated by changes in the properties and size of the central tunnel and how the changing pattern of protein–capsid interactions across a symmetry-mismatched interface can facilitate these dynamic processes.

scholarly journals Cryo-EM structure in situ reveals a molecular switch that safeguards virus against genome loss

eLife ◽  
2020 ◽  
Vol 9 ◽  
Author(s):  
Oliver W Bayfield ◽  
Alasdair C Steven ◽  
Alfred A Antson
Keyword(s):  
Protein Interactions ◽  
Bound State ◽  
Molecular Switch ◽  
Protein Protein Interactions ◽  
Genome Packaging ◽  
Dna Viruses ◽  
Portal Protein ◽  
Double Stranded Dna ◽  
Protein Functions

The portal protein is a key component of many double-stranded DNA viruses, governing capsid assembly and genome packaging. Twelve subunits of the portal protein define a tunnel, through which DNA is translocated into the capsid. It is unknown how the portal protein functions as a gatekeeper, preventing DNA slippage, whilst allowing its passage into the capsid, and how these processes are controlled. A cryo-EM structure of the portal protein of thermostable virus P23-45, determined in situ in its procapsid-bound state, indicates a mechanism that naturally safeguards the virus against genome loss. This occurs via an inversion of the conformation of the loops that define the constriction in the central tunnel, accompanied by a hydrophilic–hydrophobic switch. The structure also shows how translocation of DNA into the capsid could be modulated by a changing mode of protein–protein interactions between portal and capsid, across a symmetry-mismatched interface.

Proteolytic Control of Bacteriophage HK97 Capsid Maturation.

1998 ◽  
Vol 4 (S2) ◽  
pp. 984-985
Author(s):  
Robert L. Duda ◽  
James F. Conway ◽  
Naiqian Cheng ◽  
Alasdair C. Steven ◽  
Roger W. Hendrix
Keyword(s):  
Conformational Changes ◽  
Three Dimensional ◽  
Temperate Bacteriophage ◽  
Covalent Bonds ◽  
E Coli ◽  
Cryo Electron Microscopy ◽  
Dimensional Reconstruction ◽  
Capsid Maturation ◽  
Icosahedral Capsid ◽  
Icosahedral Particle

HK97 is a tailed temperate bacteriophage of E. coli that builds an icosahedral capsid using steps that include regulated assembly, proteolysis, radical conformational changes and the formation of novel covalent bonds (Fig. 1). This pathway is being exploited as a model system to explore how the formation of multiprotein complexes can be regulated by each of these mechanisms. We have identified and purified at least four intermediates (Prohead I, Prohead II, Head I and Head II) and examined them by cryo-electron microscopy and three dimensional reconstruction procedures (Fig. 2). Comparison of particle reconstructions at resolution of about 25 - 30 A have lead to major insights into the causes and purposes of the regulated changes that we have also characterized biochemically and genetically.Prohead I consists of 420 copies of the 42 kDa gp5 capsid protein arranged as 72 blister-shaped morphological capsomers in a thick walled hollow T=7 icosahedral particle with a diameter of -470 Å.

scholarly journals Capsid expansion of bacteriophage T5 revealed by high resolution cryoelectron microscopy

2019 ◽  
Vol 116 (42) ◽  
pp. 21037-21046 ◽  
Author(s):  
Alexis Huet ◽  
Robert L. Duda ◽  
Pascale Boulanger ◽  
James F. Conway
Keyword(s):  
Molecular Structure ◽  
High Resolution ◽  
Major Capsid Protein ◽  
Cryoelectron Microscopy ◽  
Viral Dna ◽  
Thin Walled ◽  
Capsid Maturation ◽  
High Level ◽  
Bacteriophage T5 ◽  
Icosahedral Capsid

The large (90-nm) icosahedral capsid of bacteriophage T5 is composed of 775 copies of the major capsid protein (mcp) together with portal, protease, and decoration proteins. Its assembly is a regulated process that involves several intermediates, including a thick-walled round precursor prohead that expands as the viral DNA is packaged to yield a thin-walled and angular mature capsid. We investigated capsid maturation by comparing cryoelectron microscopy (cryo-EM) structures of the prohead, the empty expanded capsid both with and without decoration protein, and the virion capsid at a resolution of 3.8 Å for the latter. We detail the molecular structure of the mcp, its complex pattern of interactions, and their evolution during maturation. The bacteriophage T5 mcp is a variant of the canonical HK97-fold with a high level of plasticity that allows for the precise assembly of a giant macromolecule and the adaptability needed to interact with other proteins and the packaged DNA.

scholarly journals Post-Translational Modifications of Retroviral HIV-1 Gag Precursors: An Overview of Their Biological Role

2021 ◽  
Vol 22 (6) ◽  
pp. 2871
Author(s):  
Charlotte Bussienne ◽  
Roland Marquet ◽  
Jean-Christophe Paillart ◽  
Serena Bernacchi
Keyword(s):  
Cellular Response ◽  
Viral Infections ◽  
Current Knowledge ◽  
Genome Packaging ◽  
Post Translational Modifications ◽  
Gag Proteins ◽  
Viral Budding ◽  
Protein Functions ◽  
Cellular Components ◽  
Hiv 1

Protein post-translational modifications (PTMs) play key roles in eukaryotes since they finely regulate numerous mechanisms used to diversify the protein functions and to modulate their signaling networks. Besides, these chemical modifications also take part in the viral hijacking of the host, and also contribute to the cellular response to viral infections. All domains of the human immunodeficiency virus type 1 (HIV-1) Gag precursor of 55-kDa (Pr55Gag), which is the central actor for viral RNA specific recruitment and genome packaging, are post-translationally modified. In this review, we summarize the current knowledge about HIV-1 Pr55Gag PTMs such as myristoylation, phosphorylation, ubiquitination, sumoylation, methylation, and ISGylation in order to figure out how these modifications affect the precursor functions and viral replication. Indeed, in HIV-1, PTMs regulate the precursor trafficking between cell compartments and its anchoring at the plasma membrane, where viral assembly occurs. Interestingly, PTMs also allow Pr55Gag to hijack the cell machinery to achieve viral budding as they drive recognition between viral proteins or cellular components such as the ESCRT machinery. Finally, we will describe and compare PTMs of several other retroviral Gag proteins to give a global overview of their role in the retroviral life cycle.

Chaperonin as the normal controls and pathological anti-stress response in the human reproductive system

2016 ◽  
pp. 126-129
Author(s):  
M. Makarenko ◽  
◽  
D. Hovsyeyev ◽  
L. Sydoryk ◽  
◽  
...  
Keyword(s):  
Reproductive System ◽  
Stress Proteins ◽  
Physiological Stress ◽  
Protein Complexes ◽  
Reproductive Function ◽  
Intercellular Signaling ◽  
Toll Like Receptors ◽  
Wide Range ◽  
Protein Functions ◽  
And Function

Different kinds of physiological stress cause mass changes in the cells, including the changes in the structure and function of the protein complexes and in separate molecules. The protein functions is determined by its folding (the spatial conclusion), which depends on the functioning of proteins of thermal shock- molecular chaperons (HSPs) or depends on the stress proteins, that are high-conservative; specialized proteins that are responsible for the correct proteinaceous folding. The family of the molecular chaperones/ chaperonins/ Hsp60 has a special place due to the its unique properties of activating the signaling cascades through the system of Toll-like receptors; it also stimulates the cells to produce anti- inflammatory cytokines, defensins, molecules of cell adhesion and the molecules of MHC; it functions as the intercellular signaling molecule. The pathological role of Hsp60 is established in a wide range of illnesses, from diabetes to atherosclerosis, where Hsp60 takes part in the regulation of both apoptosis and the autoimmune processes. The presence of the HSPs was found in different tissues that are related to the reproductive system. Key words: molecular chaperons (HSPs), Toll-like receptors, reproductive function, natural auto antibody.

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