scholarly journals Portal Protein: The Orchestrator of Capsid Assembly for the dsDNA Tailed Bacteriophages and Herpesviruses

2019 ◽  
Vol 6 (1) ◽  
pp. 141-160 ◽  
Author(s):  
Corynne L. Dedeo ◽  
Gino Cingolani ◽  
Carolyn M. Teschke
Keyword(s):  
Drug Target ◽  
Sequence Similarity ◽  
Antiviral Drug ◽  
Viral Assembly ◽  
Dna Packaging ◽  
Capsid Assembly ◽  
Portal Protein ◽  
Ring Assembly ◽  
Double Stranded Dna

Tailed, double-stranded DNA bacteriophages provide a well-characterized model system for the study of viral assembly, especially for herpesviruses and adenoviruses. A wealth of genetic, structural, and biochemical work has allowed for the development of assembly models and an understanding of the DNA packaging process. The portal complex is an essential player in all aspects of bacteriophage and herpesvirus assembly. Despite having low sequence similarity, portal structures across bacteriophages share the portal fold and maintain a conserved function. Due to their dynamic role, portal proteins are surprisingly plastic, and their conformations change for each stage of assembly. Because the maturation process is dependent on the portal protein, researchers have been working to validate this protein as a potential antiviral drug target. Here we review recent work on the role of portal complexes in capsid assembly, including DNA packaging, as well as portal ring assembly and incorporation and analysis of portal structures.

scholarly journals Cryo-EM structure and in vitro DNA packaging of a thermophilic virus with supersized T=7 capsids

2019 ◽  
Vol 116 (9) ◽  
pp. 3556-3561 ◽  
Author(s):  
Oliver W. Bayfield ◽  
Evgeny Klimuk ◽  
Dennis C. Winkler ◽  
Emma L. Hesketh ◽  
Maria Chechik ◽  
...  
Keyword(s):  
Conformational Changes ◽  
Structural Integrity ◽  
Thermus Thermophilus ◽  
Dna Packaging ◽  
Dna Viruses ◽  
Portal Protein ◽  
Single Vertex ◽  
Double Stranded Dna ◽  
Β Sheets

Double-stranded DNA viruses, including bacteriophages and herpesviruses, package their genomes into preformed capsids, using ATP-driven motors. Seeking to advance structural and mechanistic understanding, we established in vitro packaging for a thermostable bacteriophage, P23-45 of Thermus thermophilus. Both the unexpanded procapsid and the expanded mature capsid can package DNA in the presence of packaging ATPase over the 20 °C to 70 °C temperature range, with optimum activity at 50 °C to 65 °C. Cryo-EM reconstructions for the mature and immature capsids at 3.7-Å and 4.4-Å resolution, respectively, reveal conformational changes during capsid expansion. Capsomer interactions in the expanded capsid are reinforced by formation of intersubunit β-sheets with N-terminal segments of auxiliary protein trimers. Unexpectedly, the capsid has T=7 quasi-symmetry, despite the P23-45 genome being twice as large as those of known T=7 phages, in which the DNA is compacted to near-crystalline density. Our data explain this anomaly, showing how the canonical HK97 fold has adapted to double the volume of the capsid, while maintaining its structural integrity. Reconstructions of the procapsid and the expanded capsid defined the structure of the single vertex containing the portal protein. Together with a 1.95-Å resolution crystal structure of the portal protein and DNA packaging assays, these reconstructions indicate that capsid expansion affects the conformation of the portal protein, while still allowing DNA to be packaged. These observations suggest a mechanism by which structural events inside the capsid can be communicated to the outside.

scholarly journals The Mycoplasma gallisepticum Virulence Factor Lipoprotein MslA Is a Novel Polynucleotide Binding Protein

2013 ◽  
Vol 81 (9) ◽  
pp. 3220-3226 ◽  
Author(s):  
Yumiko Masukagami ◽  
Kelly A. Tivendale ◽  
Karim Mardani ◽  
Idan Ben-Barak ◽  
Philip F. Markham ◽  
...  
Keyword(s):  
Sequence Similarity ◽  
Mycoplasma Gallisepticum ◽  
Gene Encoding ◽  
Significant Sequence Similarity ◽  
Content Type ◽  
Double Stranded Dna ◽  
Biochemical Function ◽  
Predicted Binding Site

ABSTRACTAlthough lipoproteins of mycoplasmas are thought to play a crucial role in interactions with their hosts, very few have had their biochemical function defined. The gene encoding the lipoprotein MslA inMycoplasma gallisepticumhas recently been shown to be required for virulence, but the biochemical function of this gene is not known. Although this gene has no significant sequence similarity to any gene of known function, it is located within an operon inM. gallisepticumthat contains a homolog of a gene previously shown to be a nonspecific exonuclease. We mutagenized both genes to facilitate expression inEscherichia coliand then examined the functions of the recombinant proteins. The capacity of MslA to bind polynucleotides was examined, and we found that the protein bound single- and double-stranded DNA, as well as single-stranded RNA, with a predicted binding site of greater than 1 nucleotide but less than or equal to 5 nucleotides in length. Recombinant MslA cleaved into two fragmentsin vitro, both of which were able to bind oligonucleotides. These findings suggest that the role of MslA may be to act in concert with the lipoprotein nuclease to generate nucleotides for transport into the mycoplasma cell, as the remaining genes in the operon are predicted to encode an ABC transporter.

scholarly journals Intravirion DNA Can Access the Space Occupied by the Bacteriophage P22 Ejection Proteins

Viruses ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1504
Author(s):  
Justin C. Leavitt ◽  
Eddie B. Gilcrease ◽  
Brianna M. Woodbury ◽  
Carolyn M. Teschke ◽  
Sherwood R. Casjens
Keyword(s):  
Dna Packaging ◽  
Bacteriophage P22 ◽  
Portal Protein ◽  
Dna Molecule ◽  
Double Stranded Dna ◽  
Phage P22

Tailed double-stranded DNA bacteriophages inject some proteins with their dsDNA during infection. Phage P22 injects about 12, 12, and 30 molecules of the proteins encoded by genes 7, 16 and 20, respectively. After their ejection from the virion, they assemble into a trans-periplasmic conduit through which the DNA passes to enter the cytoplasm. The location of these proteins in the virion before injection is not well understood, although we recently showed they reside near the portal protein barrel in DNA-filled heads. In this report we show that when these proteins are missing from the virion, a longer than normal DNA molecule is encapsidated by the P22 headful DNA packaging machinery. Thus, the ejection proteins occupy positions within the virion that can be occupied by packaged DNA when they are absent.

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 Potential Dual Role of West Nile Virus NS2B in Orchestrating NS3 Enzymatic Activity in Viral Replication

Viruses ◽  
2021 ◽  
Vol 13 (2) ◽  
pp. 216
Author(s):  
Alanna C. Tseng ◽  
Vivek R. Nerurkar ◽  
Kabi R. Neupane ◽  
Helmut Kae ◽  
Pakieli H. Kaufusi
Keyword(s):  
West Nile Virus ◽  
Enzymatic Activity ◽  
Nonstructural Protein ◽  
Antiviral Drug ◽  
West Nile ◽  
Biochemical Assays ◽  
In Trans ◽  
Viral Polyprotein ◽  
Ns3 Protease

West Nile virus (WNV) nonstructural protein 3 (NS3) harbors the viral triphosphatase and helicase for viral RNA synthesis and, together with NS2B, constitutes the protease responsible for polyprotein processing. NS3 is a soluble protein, but it is localized to specialized compartments at the rough endoplasmic reticulum (RER), where its enzymatic functions are essential for virus replication. However, the mechanistic details behind the recruitment of NS3 from the cytoplasm to the RER have not yet been fully elucidated. In this study, we employed immunofluorescence and biochemical assays to demonstrate that NS3, when expressed individually and when cleaved from the viral polyprotein, is localized exclusively to the cytoplasm. Furthermore, NS3 appeared to be peripherally recruited to the RER and proteolytically active when NS2B was provided in trans. Thus, we provide evidence for a potential additional role for NS2B in not only serving as the cofactor for the NS3 protease, but also in recruiting NS3 from the cytoplasm to the RER for proper enzymatic activity. Results from our study suggest that targeting the interaction between NS2B and NS3 in disrupting the NS3 ER localization may be an attractive avenue for antiviral drug discovery.

Role of TRPM2 in brain tumours and potential as a drug target

2021 ◽  
Author(s):  
Delphine Ji ◽  
Zheng-wei Luo ◽  
Andrea Ovcjak ◽  
Rahmah Alanazi ◽  
Mei-Hua Bao ◽  
...  
Keyword(s):  
Brain Tumours ◽  
Drug Target

scholarly journals Cytosolic Ribosomal Mutations That Abolish Accumulation of Circular Intron in the Mitochondria Without Preventing Senescence of Podospora anserina

Genetics ◽  
1997 ◽  
Vol 145 (3) ◽  
pp. 697-705 ◽  
Author(s):  
Philippe Silar ◽  
France Koll ◽  
Michèle Rossignol
Keyword(s):  
Mitochondrial Dna ◽  
Ribosomal Proteins ◽  
Podospora Anserina ◽  
Cox1 Gene ◽  
Accuracy Control ◽  
Additional Function ◽  
Mutant Proteins ◽  
Double Stranded Dna ◽  
Dna Modifications

The filamentous fungus Podospora anserina presents a degeneration syndrome called Senescence associated with mitochondrial DNA modifications. We show that mutations affecting the two different and interacting cytosolic ribosomal proteins (S7 and S19) systematically and specifically prevent the accumulation of senDNAα (a circular double-stranded DNA plasmid derived from the first intron of the mitochondrial cox1 gene or intron α) without abolishing Senescence nor affecting the accumulation of other usually observed mitochondrial DNA rearrangements. One of the mutant proteins is homologous to the Escherichia coli S4 and Saccharomyces cerevisiae S13 ribosomal proteins, known to be involved in accuracy control of cytosolic translation. The lack of accumulation of senDNAα seems to result from a nontrivial ribosomal alteration unrelated to accuracy control, indicating that S7 and S19 proteins have an additional function. The results strongly suggest that modified expression of nucleus-encoded proteins contributes to Senescence in P. anserina. These data do not fit well with some current models, which propose that intron α plays the role of the cytoplasmic and infectious Determinant of Senescence that was defined in early studies.

scholarly journals Occurrence of drug target residues within decantation tank sediments: a good clue to assess their historical excretion?

2021 ◽  
Vol 31 (1) ◽  
Author(s):  
Thomas Thiebault ◽  
Laëtitia Fougère ◽  
Anaëlle Simonneau ◽  
Emilie Destandau ◽  
Claude Le Milbeau ◽  
...  
Keyword(s):  
Drug Target ◽  
Chemical Properties ◽  
Deposition Process ◽  
Drug Consumption ◽  
Organic Layers ◽  
Sewer Systems ◽  
Physico Chemical ◽  
Deep Underground ◽  
Deposition Processes

AbstractThis study investigated the potential of sediments accumulated in sewer systems to record human activities through the occurrence of drug target residues (DTR). The installation studied is 17 m deep underground decantation tank that traps the coarse fractions of a unitary sewer system (northern part of Orléans, France), collecting both stormwater and wastewater. The sediments deposited in this tank could constitute a nonesuch opportunity to study the historical evolution of illicit and licit drug consumption in the catchment, however, the deposition processes and the record of DTRs remain largely unknown at present. Five cores were acquired from 2015 to 2017. One hundred fifty-two sediment samples were extracted using a mixture of ultra-pure water:methanol (1:1) prior to analysis of the extracts by high-pressure liquid chromatography coupled to tandem mass spectrometry. Several classical sedimentological analyses such as total organic carbon, facies description and granulometry were also performed on these samples, in order to understand the most important factors (e.g., physico-chemical properties of the DTRs, solid type, assumed load in wastewater) impacting their deposition.The key role of the speciation of DTRs was highlighted by the higher contents in neutral and anionic DTRs in organic layers, whereas only cationic DTRs were found in mineral layers. The considerable modifications in the sediments’ properties, generated by distinct origins (i.e., stormwater or wastewater), are therefore the most important drivers that must be taken into account when back-calculating the historical patterns of drug consumption from their DTR concentrations in decantation tank sediments. Further research remains necessary to fully understand the deposition process, but this study provides new clues explaining these temporal evolutions.

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