scholarly journals Human immunodeficiency virus-1 BF intersubtype recombinant viral protein U second alpha helix plays an important role in viral release and BST-2 degradation

2013 ◽  
Vol 94 (4) ◽  
pp. 758-766 ◽  
Author(s):  
Cristian De Candia ◽  
Constanza Espada ◽  
Gabriel Duette ◽  
Horacio Salomón ◽  
Mauricio Carobene
Keyword(s):  
Viral Protein ◽  
Transmembrane Domain ◽  
Alpha Helix ◽  
Protein Variant ◽  
Viral Release ◽  
Subtype B ◽  
Viral Protein U ◽  
Intersubtype Recombination ◽  
Α Helix ◽  
The Impact

We previously reported a naturally occurring BF intersubtype recombinant viral protein U (Vpu) variant with an augmented capacity to enhance viral replication. Structural analysis of this variant revealed that its transmembrane domain and α-helix I in the cytoplasmic domain (CTD) corresponded to subtype B, whereas the α-helix II in the CTD corresponded to subtype F1. In this study, we aimed to evaluate the role of the Vpu cytoplasmic α-helix II domain in viral release enhancement and in the down-modulation of BST-2 and CD4 from the cell surface. In addition, as serine residues in Vpu amino acid positions 61 or 64 have been shown to regulate Vpu intracellular half-life, which in turn could influence the magnitude of viral release, we also studied the impact of these residues on the VpuBF functions, since S61 and S64 are infrequently found among BF recombinant Vpu variants. Our results showed that the exchange of Vpu α-helix II between subtypes (B→F) directly correlated with the enhancement of viral release and, to a lesser extent, with changes in the capacity of the resulting chimera to down-modulate BST-2 and CD4. No differences in viral release and BST-2 down-modulation were observed between VpuBF and VpuBF-E61S. On the other hand, VpuBF-A64S showed a slightly reduced capacity to enhance viral production, but was modestly more efficient than VpuBF in down-modulating BST-2. In summary, our observations clearly indicate that α-helix II is actively involved in Vpu viral-release-promoting activity and that intersubtype recombination between subtypes B and F1 created a protein variant with a higher potential to boost the spread of the recombinant strain that harbours it.

ALPHA-HELIX FORMATION IN C-PEPTIDE RNASE-A INVESTIGATED BY PARALLEL TEMPERING SIMULATIONS

2007 ◽  
Vol 18 (01) ◽  
pp. 91-98 ◽  
Author(s):  
GÖKHAN GÖKOĞLU ◽  
TARIK ÇELİK
Keyword(s):  
Energy State ◽  
Minimum Energy ◽  
Alpha Helix ◽  
Salt Bridge ◽  
Rnase A ◽  
Parallel Tempering ◽  
Implicit Solvent ◽  
C Peptide ◽  
Helix Formation ◽  
Α Helix

We have performed parallel tempering simulations of a 13-residue peptide fragment of ribonuclease-A, c-peptide, in implicit solvent with constant dielectric permittivity. This peptide has a strong tendency to form α-helical conformations in solvent as suggested by circular dichroism (CD) and nuclear magnetic resonance (NMR) experiments. Our results demonstrate that 5th and 8–12 residues are in the α-helical region of the Ramachandran map for global minimum energy state in solvent environment. Effects of salt bridge formation on stability of α-helix structure are discussed.

scholarly journals Canine Influenza Virus is Mildly Restricted by Canine Tetherin Protein

Viruses ◽  
2018 ◽  
Vol 10 (10) ◽  
pp. 565
Author(s):  
Yun Zheng ◽  
Xiangqi Hao ◽  
Qingxu Zheng ◽  
Xi Lin ◽  
Xin Zhang ◽  
...  
Keyword(s):  
Influenza Virus ◽  
Transmembrane Domain ◽  
Transmembrane Protein ◽  
Cellular Damage ◽  
Interferon Response ◽  
Type I ◽  
Canine Influenza Virus ◽  
Immune Factor ◽  
Canine Influenza ◽  
The Impact

Tetherin (BST2/CD317/HM1.24) has emerged as a key host-cell ·defence molecule that acts by inhibiting the release and spread of diverse enveloped virions from infected cells. We analysed the biological features of canine tetherin and found it to be an unstable hydrophilic type I transmembrane protein with one transmembrane domain, no signal peptide, and multiple glycosylation and phosphorylation sites. Furthermore, the tissue expression profile of canine tetherin revealed that it was particularly abundant in immune organs. The canine tetherin gene contains an interferon response element sequence that can be regulated and expressed by canine IFN-α. A CCK-8 assay showed that canine tetherin was effective in helping mitigate cellular damage caused by canine influenza virus (CIV) infection. Additionally, we found that the overexpression of canine tetherin inhibited replication of the CIV and that interference with the canine tetherin gene enhanced CIV replication in cells. The impact of canine tetherin on CIV replication was mild. However, these results elucidate the role of the innate immune factor, canine tetherin, during CIV infection for the first time.

scholarly journals Reversible transition between α-helix and β-sheet conformation of a transmembrane domain

2009 ◽  
Vol 1788 (9) ◽  
pp. 1722-1730 ◽  
Author(s):  
Wissam Yassine ◽  
Nada Taib ◽  
Silvina Federman ◽  
Alexandra Milochau ◽  
Sabine Castano ◽  
...  
Keyword(s):  
Transmembrane Domain ◽  
Reversible Transition ◽  
Α Helix ◽  
Β Sheet

scholarly journals The role of prolines and glycine in the transmembrane domain of LAT

2020 ◽  
Author(s):  
Daniela Glatzová ◽  
Harsha Mavila ◽  
Maria Chiara Saija ◽  
Tomáš Chum ◽  
Lukasz Cwiklik ◽  
...  
Keyword(s):  
Amino Acids ◽  
Plasma Membrane ◽  
Transmembrane Domain ◽  
Transmembrane Helix ◽  
Helical Structure ◽  
Surface Expression ◽  
Transmembrane Segment ◽  
Proline Residue ◽  
And Function ◽  
The Impact

ABSTRACTLAT is a critical regulator of T cell development and function. It organises signalling events at the plasma membrane. However, the mechanism, which controls LAT localisation at the plasma membrane is not fully understood. Here, we studied the impact of helix-breaking amino acids, two prolines and one glycine, in the transmembrane segment on localisation and function of LAT. Using in silico analysis, confocal and superresolution imaging and flow cytometry we demonstrate that central proline residue destabilises transmembrane helix by inducing a kink. The helical structure and dynamics is further regulated by glycine and another proline residue in the luminal part of LAT transmembrane domain. Replacement of these residues with aliphatic amino acids reduces LAT dependence on palmitoylation for sorting to the plasma membrane. However, surface expression of these mutants is not sufficient to recover function of non-palmitoylated LAT in stimulated T cells. These data indicate that geometry and dynamics of LAT transmembrane segment regulate its localisation and function in immune cells.

scholarly journals Mutational analysis of HIV-1 viral protein U at Ser52 and Ser56 among the HIV-1 infected patients of Manipur

2016 ◽  
Vol 15 (1) ◽  
pp. 42-46
Author(s):  
Adhikarimayum Lakhikumar Sharma ◽  
Thiyam Ramsing Singh ◽  
Khuraijam Ranjana Devi ◽  
Lisam Shanjukumar Singh
Keyword(s):  
Viral Protein ◽  
Mutational Analysis ◽  
Viral Protein U ◽  
Hiv 1

scholarly journals Positive Charges Determine the Topology and Functionality of the Transmembrane Domain in the Chloroplastic Outer Envelope Protein Toc34

1998 ◽  
Vol 141 (4) ◽  
pp. 895-904 ◽  
Author(s):  
Timo May ◽  
Jürgen Soll
Keyword(s):  
Envelope Protein ◽  
Transmembrane Domain ◽  
Protein Translocation ◽  
Small Subunit ◽  
Lipid Phase ◽  
Outer Envelope ◽  
Double Positive ◽  
Membrane Anchor ◽  
Bisphosphate Carboxylase ◽  
Α Helix

The chloroplastic outer envelope protein Toc34 is inserted into the membrane by a COOH-terminal membrane anchor domain in the orientation Ncyto-Cin. The insertion is independent of ATP and a cleavable transit sequence. The cytosolic domain of Toc34 does not influence the insertion process and can be replaced by a different hydrophilic reporter peptide. Inversion of the COOH-terminal, 45-residue segment, including the membrane anchor domain (Toc34Cinv), resulted in an inverted topology of the protein, i.e., Nin-Ccyto. A mutual exchange of the charged amino acid residues NH2- and COOH-proximal of the hydrophobic α-helix indicates that a double-positive charge at the cytosolic side of the transmembrane α-helix is the sole determinant for its topology. When the inverted COOH-terminal segment was fused to the chloroplastic precursor of the ribulose-1,5-bisphosphate carboxylase small subunit (pS34Cinv), it engaged the transit sequence–dependent import pathway. The inverted peptide domain of Toc34 functions as a stop transfer signal and is released out of the outer envelope protein translocation machinery into the lipid phase. Simultaneously, the NH2-terminal part of the hybrid precursor remained engaged in the inner envelope protein translocon, which could be reversed by the removal of ATP, demonstrating that only an energy-dependent force but no further ionic interactions kept the precursor in the import machinery.

scholarly journals Conformational rearrangements in the transmembrane domain of CNGA1 channels revealed by single-molecule force spectroscopy

2015 ◽  
Vol 6 (1) ◽  
Author(s):  
Sourav Maity ◽  
Monica Mazzolini ◽  
Manuel Arcangeletti ◽  
Alejandro Valbuena ◽  
Paolo Fabris ◽  
...  
Keyword(s):  
Single Molecule ◽  
Conformational Changes ◽  
Transmembrane Domain ◽  
Force Spectroscopy ◽  
Dynamic Structure ◽  
Transmembrane Domains ◽  
Structural Studies ◽  
Single Molecule Force Spectroscopy ◽  
Conformational Rearrangements ◽  
Α Helix

Abstract Cyclic nucleotide-gated (CNG) channels are activated by binding of cyclic nucleotides. Although structural studies have identified the channel pore and selectivity filter, conformation changes associated with gating remain poorly understood. Here we combine single-molecule force spectroscopy (SMFS) with mutagenesis, bioinformatics and electrophysiology to study conformational changes associated with gating. By expressing functional channels with SMFS fingerprints in Xenopus laevis oocytes, we were able to investigate gating of CNGA1 in a physiological-like membrane. Force spectra determined that the S4 transmembrane domain is mechanically coupled to S5 in the open state, but S3 in the closed state. We also show there are multiple pathways for the unfolding of the transmembrane domains, probably caused by a different degree of α-helix folding. This approach demonstrates that CNG transmembrane domains have dynamic structure and establishes SMFS as a tool for probing conformational change in ion channels.

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