scholarly journals Elicitation of superinfection exclusion by p28 of turnip crinkle virus is separable from its replication function with mutations at specific amino acid residues

2019 ◽  
Author(s):  
Qin Guo ◽  
Shaoyan Zhang ◽  
Rong Sun ◽  
Xiaolong Yao ◽  
Xiao-Feng Zhang ◽  
...  
Keyword(s):  
Amino Acid ◽  
Single Amino Acid ◽  
Amino Acid Residues ◽  
Turnip Crinkle Virus ◽  
Virus Infections ◽  
Superinfection Exclusion ◽  
Protein Levels ◽  
Infected Cells ◽  
Concentration Threshold ◽  
Replication Function

ABSTRACTWe recently reported that the p28 auxiliary replication protein encoded by turnip crinkle virus (TCV) is also responsible for eliciting superinfection exclusion (SIE) against superinfecting TCV. However, it remains unresolved whether the replication function of p28 could be separated from its ability to elicit SIE. Here we report the identification of two single amino acid (aa) mutations that decouple these two functions. Using an Agrobacterium infiltration-based delivery system, we transiently expressed a series of p28 deletion and point mutants, and tested their ability to elicit SIE against a co-introduced TCV replicon. We found that substituting alanine (A) for valine (V) and phenylalanine (F) at p28 positions 181 and 182, respectively, modestly compromised SIE in transiently expressed p28 derivatives. Upon incorporation into TCV replicons, V181A and F182A decoupled TCV replication and SIE diametrically. While V181A impaired SIE without detectably compromising replication, F182A abolished TCV replication but had no effect on SIE once the replication of the defective replicon was restored through complementation. Both mutations diminished accumulation of p28 protein, suggesting that p28 must reach a concentration threshold in order to elicit a strong SIE. Importantly, the severe reduction of F182A protein levels correlated with a dramatic loss in the number of intracellular p28 foci formed by p28-p28 interactions. Together these findings not only decouples the replication and SIE functions of p28, but also unveils a concentration dependence for p28 coalescence and SIE elicitation. These data further highlight the role of p28 multimerization in driving the exclusion of secondary TCV infections.IMPORTANCESuperinfection exclusion (SIE) insulates virus-infected cells from subsequent invasion by the same or closely related viruses. SIE has been observed in both animal and plant virus-infected cells. Therefore, a thorough understanding of how SIE is achieved at the molecular level is expected to inspire novel strategies for combating virus infections in humans, animals, and plants. Our group has been using turnip crinkle virus (TCV) to elucidate the molecular interactions critical for SIE elicitation. The current study builds on the previous observation that TCV SIE is elicited by one single TCV-encoded protein (p28), and further identifies key regions and amino acids that are needed for SIE. We unravel key amino acid changes that decouple the replication and SIE functions of p28, and provides novel mechanistic insights of SIE.

scholarly journals Superinfection Exclusion by p28 of Turnip Crinkle Virus Is Separable from Its Replication Function

2020 ◽  
Vol 33 (2) ◽  
pp. 364-375
Author(s):  
Qin Guo ◽  
Shaoyan Zhang ◽  
Rong Sun ◽  
Xiaolong Yao ◽  
Xiao-Feng Zhang ◽  
...  
Keyword(s):  
Amino Acid ◽  
Single Amino Acid ◽  
Turnip Crinkle Virus ◽  
Superinfection Exclusion ◽  
Protein Levels ◽  
Severe Reduction ◽  
Amino Acid Mutations ◽  
Concentration Threshold ◽  
Replication Function

We recently reported that the p28 auxiliary replication protein encoded by turnip crinkle virus (TCV) is also responsible for eliciting superinfection exclusion (SIE) against superinfecting TCV. However, it remains unresolved whether the replication function of p28 could be separated from its ability to elicit SIE. Here, we report the identification of two single amino acid mutations that decouple these two functions. Using an Agrobacterium infiltration-based delivery system, we transiently expressed a series of p28 deletion and point mutants, and tested their ability to elicit SIE against a cointroduced TCV replicon. We found that substituting alanine (A) for valine (V) and phenylalanine (F) at p28 positions 181 and 182, respectively, modestly compromised SIE in transiently expressed p28 derivatives. Upon incorporation into TCV replicons, V181A and F182A decoupled TCV replication and SIE diametrically. Although V181A impaired SIE without detectably compromising replication, F182A abolished TCV replication but had no effect on SIE once the replication of the defective replicon was restored through complementation. Both mutations diminished accumulation of p28 protein, suggesting that p28 must reach a concentration threshold in order to elicit a strong SIE. Importantly, the severe reduction of F182A protein levels correlated with a dramatic loss in the number of intracellular p28 foci formed by p28–p28 interactions. Together, these findings not only decouple the replication and SIE functions of p28 but also unveil a concentration dependence for p28 coalescence and SIE elicitation. These data further highlight the role of p28 multimerization in driving the exclusion of secondary TCV infections.

scholarly journals Identification of critical amino acid residues in the regulatory N-terminal domain of PMEL

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Susan M. Mitchell ◽  
Morven Graham ◽  
Xinran Liu ◽  
Ralf M. Leonhardt
Keyword(s):  
Amino Acid ◽  
Pigment Cell ◽  
Specific Protein ◽  
Single Amino Acid ◽  
Amyloid Formation ◽  
Amino Acid Residues ◽  
Proteolytic Fragment ◽  
The Core ◽  
N Terminus ◽  
In Cis

AbstractThe pigment cell-specific protein PMEL forms a functional amyloid matrix in melanosomes onto which the pigment melanin is deposited. The amyloid core consists of a short proteolytic fragment, which we have termed the core-amyloid fragment (CAF) and perhaps additional parts of the protein, such as the PKD domain. A highly O-glycosylated repeat (RPT) domain also derived from PMEL proteolysis associates with the amyloid and is necessary to establish the sheet-like morphology of the assemblies. Excluded from the aggregate is the regulatory N-terminus, which nevertheless must be linked in cis to the CAF in order to drive amyloid formation. The domain is then likely cleaved away immediately before, during, or immediately after the incorporation of a new CAF subunit into the nascent amyloid. We had previously identified a 21 amino acid long region, which mediates the regulatory activity of the N-terminus towards the CAF. However, many mutations in the respective segment caused misfolding and/or blocked PMEL export from the endoplasmic reticulum, leaving their phenotype hard to interpret. Here, we employ a saturating mutagenesis approach targeting the motif at single amino acid resolution. Our results confirm the critical nature of the PMEL N-terminal region and identify several residues essential for PMEL amyloidogenesis.

scholarly journals Identification of naturally processed viral nonapeptides allows their quantification in infected cells and suggests an allele-specific T cell epitope forecast.

1991 ◽  
Vol 174 (2) ◽  
pp. 425-434 ◽  
Author(s):  
K Falk ◽  
O Rötzschke ◽  
K Deres ◽  
J Metzger ◽  
G Jung ◽  
...  
Keyword(s):  
Amino Acid ◽  
T Cell ◽  
Synthetic Peptides ◽  
Cell Epitope ◽  
Reversed Phase ◽  
T Cell Epitope ◽  
Amino Acid Residues ◽  
Allele Specific ◽  
Infected Cells ◽  
Natural Peptides

Virus-specific cytotoxic T lymphocytes (CTL) recognize virus-derived peptides presented by major histocompatibility complex (MHC) class I molecules on virus-infected cells. Such peptides have been isolated from infected cells and were compared to synthetic peptides. We found previously the Kd- or Db-restricted natural influenza nucleoprotein peptides to coelute on reversed phase high performance liquid chromatography columns with certain peptidic by-products present in synthetic peptide preparations. Here we show by extensive biochemical and immunological comparison that the natural peptides in all respects behave as the surmised synthetic nonapeptides, and thus, must be identical to them. The absolute amounts of these natural peptides contained in infected cells could be determined to be between 220 and 540 copies by comparing with defined amounts of pure synthetic nonapeptides. The comparison of the natural Kd-restricted peptide with published synthetic peptides known to contain other Kd-restricted CTL epitopes suggested a new MHC allele-specific T cell epitope forecast method, based on the defined length of nine amino acid residues and on critical amino acid residues at the second and the last position.

A Mutation in the  Subunit of the Platelet Integrin IIbβ3 Identifies a Novel Region Important for Ligand Binding

Blood ◽  
1999 ◽  
Vol 93 (3) ◽  
pp. 918-924 ◽  
Author(s):  
Eileen Collins Tozer ◽  
Elizabeth K. Baker ◽  
Mark H. Ginsberg ◽  
Joseph C. Loftus
Keyword(s):  
Amino Acid ◽  
Ligand Binding ◽  
Single Amino Acid ◽  
Chimeric Receptor ◽  
Amino Acid Residues ◽  
Genetic Approach ◽  
Specific Amino Acid ◽  
Transfected Cells ◽  
Binding Function ◽  
A Cell

Abstract An unbiased genetic approach was used to identify a specific amino acid residue in the IIb subunit important for the ligand binding function of the integrin IIbβ. Chemically mutagenized cells were selected by flow cytometry based on their inability to bind the ligand mimetic antibody PAC1 and a cell line containing a single amino acid substitution in IIb at position 224 (D→V) was identified. Although well expressed on the surface of transfected cells, IIbD224Vβ3 as well as IIbD224Aβ3 did not bind IIbβ3-specific ligands or a RGD peptide, a ligand shared in common with vβ3. Insertion of exon 5 of IIb, residues G193-W235, into the backbone of the v subunit did not enable the chimeric receptor to bind IIbβ3-specific ligands. However, the chimeric receptor was still capable of binding to a RGD affinity matrix. IIbD224 is not well conserved among other integrin  subunits and is located in a region of significant variability. In addition, amino acid D224 lies within a predicted loop of the recently proposed β-propeller model for integrin  subunits and is adjacent to a loop containing amino acid residues previously implicated in receptor function. These data support a role for this region in ligand binding function of the IIbβ3 receptor.

scholarly journals Amino Acid Residues in the Carboxy-Terminal Region of Cottontail Rabbit Papillomavirus E6 Influence Spontaneous Regression of Cutaneous Papillomas

2002 ◽  
Vol 76 (23) ◽  
pp. 11801-11808 ◽  
Author(s):  
Jiafen Hu ◽  
Nancy M. Cladel ◽  
Martin D. Pickel ◽  
Neil D. Christensen
Keyword(s):  
Amino Acid ◽  
Immune Responses ◽  
Single Amino Acid ◽  
Human Populations ◽  
Amino Acid Residues ◽  
High Frequencies ◽  
Host Immune Responses ◽  
Cottontail Rabbit ◽  
Single Amino Acid Change ◽  
Carboxy Terminal

ABSTRACT Previous studies have identified two different strains of cottontail rabbit papillomavirus (CRPV) that differ by approximately 5% in base pair sequence and that perform quite differently when used to challenge New Zealand White (NZW) rabbit skin. One strain caused persistent lesions (progressor strain), and the other induced papillomas that spontaneously regressed (regressor strain) at high frequencies (J. Salmon, M. Nonnenmacher, S. Caze, P. Flamant, O. Croissant, G. Orth, and F. Breitburd, J. Virol. 74:10766-10777, 2000; J. Salmon, N. Ramoz, P. Cassonnet, G. Orth, and F. Breitburd, Virology 235:228-234, 1997). We generated a panel of CRPV genomes that contained chimeric and mutant progressor and regressor strain E6 genes and assessed the outcome upon infection of both outbred and EIII/JC inbred NZW rabbits. The carboxy-terminal 77-amino-acid region of the regressor CRPV strain E6, which contained 15 amino acid residues that are different from those of the equivalent region of the persistent CRPV strain E6, played a dominant role in the conversion of the persistent CRPV strain to one showing high rates of spontaneous regressions. In addition, a single amino acid change (G252E) in the E6 protein of the CRPV progressor strain led to high frequencies of spontaneous regressions in inbred rabbits. These observations imply that small changes in the amino acid sequences of papillomavirus proteins can dramatically impact the outcome of natural host immune responses to these viral infections. The data imply that intrastrain differences between separate isolates of a single papillomavirus type (such as human papillomavirus type 16) may contribute to a collective variability in host immune responses in outbred human populations.

scholarly journals The Respiratory Syncytial Virus M2-1 Protein Forms Tetramers and Interacts with RNA and P in a Competitive Manner

2009 ◽  
Vol 83 (13) ◽  
pp. 6363-6374 ◽  
Author(s):  
Thi-Lan Tran ◽  
Nathalie Castagné ◽  
Virginie Dubosclard ◽  
Sylvie Noinville ◽  
Emmanuelle Koch ◽  
...  
Keyword(s):  
Respiratory Syncytial Virus ◽  
Amino Acid ◽  
Rna Binding ◽  
Amino Acid Residues ◽  
Polymerase Complex ◽  
Bacterial Rna ◽  
Infected Cells ◽  
Syncytial Virus ◽  
Α Helix ◽  
Zinc Binding Domain

ABSTRACT The respiratory syncytial virus (RSV) M2-1 protein is an essential cofactor of the viral RNA polymerase complex and functions as a transcriptional processivity and antitermination factor. M2-1, which exists in a phosphorylated or unphosphorylated form in infected cells, is an RNA-binding protein that also interacts with some of the other components of the viral polymerase complex. It contains a CCCH motif, a putative zinc-binding domain that is essential for M2-1 function, at the N terminus. To gain insight into its structural organization, M2-1 was produced as a recombinant protein in Escherichia coli and purified to >95% homogeneity by using a glutathione S-transferase (GST) tag. The GST-M2-1 fusion proteins were copurified with bacterial RNA, which could be eliminated by a high-salt wash. Circular dichroism analysis showed that M2-1 is largely α-helical. Chemical cross-linking, dynamic light scattering, sedimentation velocity, and electron microscopy analyses led to the conclusion that M2-1 forms a 5.4S tetramer of 89 kDa and ∼7.6 nm in diameter at micromolar concentrations. By using a series of deletion mutants, the oligomerization domain of M2-1 was mapped to a putative α-helix consisting of amino acid residues 32 to 63. When tested in an RSV minigenome replicon system using a luciferase gene as a reporter, an M2-1 deletion mutant lacking this region showed a significant reduction in RNA transcription compared to wild-type M2-1, indicating that M2-1 oligomerization is essential for the activity of the protein. We also show that the region encompassing amino acid residues 59 to 178 binds to P and RNA in a competitive manner that is independent of the phosphorylation status of M2-1.

scholarly journals Molecular Insights Into the Gating Kinetics of the Cardiac hERG Channel, Illuminated by Structure and Molecular Dynamics

2021 ◽  
Vol 12 ◽  
Author(s):  
Zheng Zequn ◽  
Lian Jiangfang
Keyword(s):  
Molecular Dynamics ◽  
Amino Acid ◽  
Molecular Dynamics Simulation ◽  
Dynamics Simulation ◽  
Herg Channel ◽  
Single Amino Acid ◽  
Delayed Rectifier ◽  
Amino Acid Residues ◽  
Structural Domains ◽  
Gating Kinetics

The rapidly activating delayed rectifier K+ current generated by the cardiac hERG potassium channel encoded by KCNH2 is the most important reserve current for cardiac repolarization. The unique inward rectification characteristics of the hERG channel depend on the gating regulation, which involves crucial structural domains and key single amino acid residues in the full-length hERG channel. Identifying critical molecules involved in the regulation of gating kinetics for the hERG channel requires high-resolution structures and molecular dynamics simulation models. Based on the latest progress in hERG structure and molecular dynamics simulation research, summarizing the molecules involved in the changes in the channel state helps to elucidate the unique gating characteristics of the channel and the reason for its high affinity to cardiotoxic drugs. In this review, we aim to summarize the significant advances in understanding the voltage gating regulation of the hERG channel based on its structure obtained from cryo-electron microscopy and computer simulations, which reveal the critical roles of several specific structural domains and amino acid residues.

A novel 14-3-3 gene is osmoregulated in gill epithelium of the euryhaline teleost Fundulus heteroclitus

2001 ◽  
Vol 204 (17) ◽  
pp. 2975-2985 ◽  
Author(s):  
Dietmar Kültz ◽  
Devulapalli Chakravarty ◽  
Tadepalli Adilakshmi
Keyword(s):  
Signal Transduction ◽  
Amino Acid ◽  
Fundulus Heteroclitus ◽  
Sea Water ◽  
Amino Acid Residues ◽  
Gill Epithelium ◽  
Protein Levels ◽  
Euryhaline Teleost ◽  
Binding Groove ◽  
High Level

SUMMARY We have cloned and analyzed the full-length coding sequence and 3′ untranslated region (UTR) of a unique 14-3-3 gene of the euryhaline teleost Fundulus heteroclitus, which we named 14-3-3.a. Phylogenetic analysis of the deduced amino acid sequence revealed that the 14-3-3.a gene product is most similar to vertebrate 14-3-3ζ and β, yet it displays considerable divergence to known classes of vertebrate 14-3-3 isoforms. The N and C termini of 14-3-3.a are the most unique regions, whereas the amino acid residues forming the amphipathic ligand-binding groove are highly conserved. F. heteroclitus 14-3-3.a mRNA expression is high in gill epithelium, moderate in intestine and brain, and low in gonads, white muscle and heart. Because 14-3-3 proteins are important molecular scaffolds and cofactors for phosphoproteins and signaling complexes, the high level of 14-3-3.a expression in gill epithelium of the euryhaline teleost F. heteroclitus suggests that it is crucial for signal transduction in gill epithelial cells. We provide evidence that 14-3-3.a is involved in osmosensory signal transduction by showing that its mRNA and protein levels in gill epithelium, but not in any other tissue analyzed, increase two- to fourfold within 24h of salinity transfer of fish from sea water to fresh water. These data are clear evidence for an important role of 14-3-3.a in the remodeling of gill epithelium during transition of euryhaline fish between plasma-hyperosmotic and plasma-hyposmotic environments.

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