scholarly journals Charged Residues in the Membrane Anchor of the Pestiviral Erns Protein Are Important for Processing and Secretion of Erns and Recovery of Infectious Viruses

Viruses ◽  
2021 ◽  
Vol 13 (3) ◽  
pp. 444
Author(s):  
Kay-Marcus Oetter ◽  
Juliane Kühn ◽  
Gregor Meyers
Keyword(s):  
Salt Bridge ◽  
Membrane Topology ◽  
Signal Peptidase ◽  
Salt Bridges ◽  
Membrane Anchor ◽  
Processing Efficiency ◽  
Virus Growth ◽  
Expression Construct ◽  
Charged Residues ◽  
Cellular Signal

The pestivirus envelope protein Erns is anchored in membranes via a long amphipathic helix. Despite the unusual membrane topology of the Erns membrane anchor, it is cleaved from the following glycoprotein E1 by cellular signal peptidase. This was proposed to be enabled by a salt bridge-stabilized hairpin structure (so-called charge zipper) formed by conserved charged residues in the membrane anchor. We show here that the exchange of one or several of these charged residues reduces processing at the Erns carboxy-terminus to a variable extend, but reciprocal mutations restoring the possibility to form salt bridges did not necessarily restore processing efficiency. When introduced into an Erns-only expression construct, these mutations enhanced the naturally occurring Erns secretion significantly, but again to varying extents that did not correlate with the number of possible salt bridges. Equivalent effects on both processing and secretion were also observed when the proteins were expressed in avian cells, which points at phylogenetic conservation of the underlying principles. In the viral genome, some of the mutations prevented recovery of infectious viruses or immediately (pseudo)reverted, while others were stable and neutral with regard to virus growth.

scholarly journals Comparative physicochemical and evolutionary study of SARS-CoV-2 and SARS with special reference to salt bridge and their microenvironment: A plausible explanation for divergency, stability and severity of SARS-CoV-2

2020 ◽  
Author(s):  
Debanjan Mitra ◽  
Aditya K. Pal ◽  
Pradeep Kumar Das Mohapatra
Keyword(s):  
Crucial Role ◽  
Protein Sequences ◽  
Salt Bridge ◽  
Extreme Conditions ◽  
Salt Bridges ◽  
Wuhan City ◽  
High Energies ◽  
The World ◽  
Charged Residues ◽  
Short Time

Abstract The occurrence of concentrated pneumonia cases in Wuhan city, Hubei province of China was first reported on December 30, 2019. Currently, it is known as COVID 19 and now it is a nightmare for the whole world. SARS CoV first reported in 2002, but not spread worldwide. After 18 years, in 2020 it reappears and spread worldwide as SARS-CoV-2 (COVID 19), the most dangerous virus creating disease in the world. Is it possible to create a favorable evolution within this short time? If possible, then what are those properties that are changed in SARS-CoV-2 to make it undefeated? What are the basic differences between SARS-CoV-2 and SARS? This study will find all those queries. Here, all protein sequences of SARS-CoV-2 and SARS are retrieved from the database to check their physicochemical, evolutionary and structural properties. Results showed that, charged residues are playing a key role in SARS-CoV-2 evolution. SARS-CoV-2 increases its polarity by the help of charged residues, not by the polar residues. Their divergence is also strictly restricted. Induction of salt bridges with their high energies makes it very stable in any extreme conditions. Microenvironment residues also play a very crucial role in its stability. Mostly residues are favorable and contribute high energies. These microenvironment residues help in protein engineering to reduce its stability and make them week. This comparative study will help to understand the evolution from SARS to SARS-CoV-2.

Salt bridges in model peptides

1988 ◽  
Vol 53 (11) ◽  
pp. 2810-2824 ◽  
Author(s):  
Ilmars Sekacis ◽  
Mark Shenderovich ◽  
Gregory Nikiforovich ◽  
Edvards Liepinš ◽  
Ludmila Polevaya ◽  
...  
Keyword(s):  
Synthetic Peptides ◽  
Salt Bridge ◽  
Peptide Bond ◽  
Space Structure ◽  
Side Chain ◽  
Amino Group ◽  
Salt Bridges ◽  
Ionic Bond ◽  
Theoretical Conformational Analysis ◽  
H Nmr

A group of synthetic peptides including Boc-Lys-Phe-X-Y, X = Ala (I, III) or Thr (II), Y = Pro (I, II) or Ala (III) was studied by means of 1H NMR spectroscopy and theoretical conformational analysis. Compound I in DMSO shows two conformers with the trans- and cis-configuration of the peptide bond Ala-Pro. The salt bridge between the Lys ε-amino group and the C-terminal carboxyl is featured by magnetic nonequivalence of the Lys CεH2 protons. The space structure of I and II was found to possess a salt bridge fixed by an unusual turn in the chain formed by the Lys side chain and the C-terminal dipeptide with the trans-peptide bond X-Pro. Since a stable ionic bond in III and in the cis-conformer of I has not been observed, its contribution to stabilization of the space structure of the peptides in DMSO appears rather small.

scholarly journals Controlling membrane barrier during bacterial type-III protein secretion

2020 ◽  
Author(s):  
Svenja Hüsing ◽  
Ulf van Look ◽  
Alina Guse ◽  
Eric J. C. Gálvez ◽  
Emmanuelle Charpentier ◽  
...  
Keyword(s):  
Conformational Changes ◽  
High Speed ◽  
Membrane Integrity ◽  
Salt Bridge ◽  
High Rate ◽  
Salt Bridges ◽  
Secretion Systems ◽  
Bacterial Flagellum ◽  
Type Iii ◽  
Membrane Barrier

Type-III secretion systems (T3SSs) of the bacterial flagellum and the evolutionarily related injectisome are capable of translocating proteins with a remarkable speed of several thousand amino acids per second. Here, we investigated how T3SSs are able to transport proteins at such a high rate while preventing the leakage of small molecules. Our mutational and evolutionary analyses demonstrate that an ensemble of conserved methionine residues at the cytoplasmic side of the T3SS channel create a deformable gasket (M-gasket) around fast-moving substrates undergoing export. The unique physicochemical features of the M-gasket are crucial to preserve the membrane barrier, to accommodate local conformational changes during active secretion, and to maintain stability of the secretion pore in cooperation with a plug domain (R-plug) and a network of salt-bridges. The conservation of the M-gasket, R-plug, and salt-bridge network suggests a universal mechanism by which the membrane integrity is maintained during high-speed protein translocation in all T3SSs.

scholarly journals Rubella Virus E2 Signal Peptide Is Required for Perinuclear Localization of Capsid Protein and Virus Assembly

2001 ◽  
Vol 75 (4) ◽  
pp. 1978-1983 ◽  
Author(s):  
Lok Man J. Law ◽  
Robert Duncan ◽  
Ali Esmaili ◽  
Hira L. Nakhasi ◽  
Tom C. Hobman
Keyword(s):  
Endoplasmic Reticulum ◽  
Capsid Protein ◽  
Signal Peptide ◽  
Rubella Virus ◽  
Virus Assembly ◽  
Signal Peptidase ◽  
Structural Proteins ◽  
Carboxy Terminus ◽  
Membrane Anchor ◽  
Polyprotein Precursor

ABSTRACT The rubella virus (RV) structural proteins capsid, E2, and E1 are synthesized as a polyprotein precursor. The signal peptide that initiates translocation of E2 into the lumen of the endoplasmic reticulum remains attached to the carboxy terminus of the capsid protein after cleavage by signal peptidase. Among togaviruses, this feature is unique to RV. The E2 signal peptide has previously been shown to function as a membrane anchor for the capsid protein. In the present study, we demonstrate that this domain is required for RV glycoprotein-dependent localization of the capsid protein to the juxtanuclear region and subsequent virus assembly at the Golgi complex.

scholarly journals Pathological turret mutations in the cardiac sodium channel cause long-range pore disruption

2021 ◽  
Author(s):  
Zaki F Habib ◽  
Manas Kohli ◽  
Samantha C Salvage ◽  
Taufiq Rahman ◽  
Christopher L-H Huang ◽  
...  
Keyword(s):  
Sodium Channel ◽  
Salt Bridge ◽  
Complex Salt ◽  
Site Directed Mutagenesis ◽  
Salt Bridges ◽  
Ion Permeability ◽  
Aromatic Residues ◽  
Functional Roles ◽  
Cardiac Sodium Channel ◽  
Channel Structures

AbstractThe voltage-gated sodium channel Nav1.5 initiates the cardiac action potential. Germline mutations that disrupt Nav1.5 activity predispose affected individuals to inherited cardiopathologies. Some of these Nav1.5 mutations alter amino acids in extracellular turret domains DII and DIII. Yet the mechanism is unclear. In the rat Nav1.5 structure determined by cryogenic electron microscopy, the wild-type residues corresponding to these mutants form a complex salt-bridge between the DII and DIII turret interface. Furthermore, adjacent aromatic residues form cation-π interactions with the complex salt-bridge. Here, we examine this region using site-directed mutagenesis, electrophysiology and in silico modeling. We confirm functional roles for the salt-bridges and the aromatic residues. We show that their disruption perturbs the geometry of both the DEKA selectivity ring and the inner pore vestibule that are crucial for sodium ion permeability. Our findings provide insights into a class of pathological mutations occurring not only in Nav1.5 but also in other sodium channel isoforms too. Our work illustrates how the sodium channel structures now being reported can be used to formulate and guide novel functional hypotheses.

scholarly journals Impact of Capsid Anchor Length and Sequential Processing on the Assembly and Infectivity of Dengue Virus

Proceedings ◽  
2020 ◽  
Vol 50 (1) ◽  
pp. 32 ◽  
Author(s):  
Oscar R. Burrone ◽  
José L. Slon Campos ◽  
Monica Poggianella ◽  
Jyoti Rana
Keyword(s):  
Dengue Virus ◽  
Signal Peptidase ◽  
Sequence Length ◽  
Processing Efficiency ◽  
Particle Assembly ◽  
Luminal Side ◽  
Cytosolic Side ◽  
Experimental Approaches ◽  
Viral Polyprotein ◽  
Ns3 Protease

: The assembly and secretion of flaviviruses are part of an elegantly regulated process. During maturation, the viral polyprotein undergoes several co- and post-translational cleavage events mediated by both viral and host proteases. Among these, sequential cleavage at the N- and C-termini of the hydrophobic capsid anchor (Ca) at the junction of C-PrM has been considered essential for the production of flaviviruses. Here, using a refined dengue pseudovirus production system, we show that Ca plays a key role in the processing efficiency of dengue virus type 2 (DENV2) structural proteins and the assembly of viral particles. The replacement of the relatively short DENV2 Ca with the homologous regions from West Nile or Zika viruses or, alternatively, the increase in its length, improved cleavage, and hence particle assembly. Furthermore, we show that the substitution of the Ca conserved proline residue (Pro-110), as alanine abolishes pseudovirus production, regardless of the Ca sequence length. Using two experimental approaches, we investigated the need for sequential cleavage (first on the cytosolic side, then on the luminal side) and found that, while cleavage at the Ca-Pr boundary is essential for the assembly of infective particles, the same is not true for cleavage at the C-Ca boundary. We show that both the mature (C) and unprocessed capsids (C-Ca) of DENV2 were equally efficient in packaging the viral RNA and in assembling the infective particles. This was further confirmed with mutants, in which cleavage at the luminal side, by the signal peptidase, occurred independently of cleavage at the cytosolic side, by the viral NS2B/NS3 protease. We thus demonstrate that, unlike other flaviviruses, DENV2 capsid does not require a cleavable Ca sequence and that sequential cleavage is not an obligatory requirement for the morphogenesis of infective particles.

scholarly journals Electrostatics in the stability and misfolding of the prion protein: salt bridges, self energy, and solvationThis paper is one of a selection of papers published in this special issue entitled “Canadian Society of Biochemistry, Molecular & Cellular Biology 52nd Annual Meeting — Protein Folding: Principles and Diseases” and has undergone the Journal's usual peer review process.

2010 ◽  
Vol 88 (2) ◽  
pp. 371-381 ◽  
Author(s):  
Will C. Guest ◽  
Neil R. Cashman ◽  
Steven S. Plotkin
Keyword(s):  
Prion Protein ◽  
Electrostatic Potential ◽  
Peer Review Process ◽  
Salt Bridge ◽  
Salt Bridges ◽  
Self Energy ◽  
Low Dielectric ◽  
The Stability ◽  
Α Helix ◽  
Electrostatic Potential Energy

Using a recently developed mesoscopic theory of protein dielectrics, we have calculated the salt bridge energies, total residue electrostatic potential energies, and transfer energies into a low dielectric amyloid-like phase for 12 species and mutants of the prion protein. Salt bridges and self energies play key roles in stabilizing secondary and tertiary structural elements of the prion protein. The total electrostatic potential energy of each residue was found to be invariably stabilizing. Residues frequently found to be mutated in familial prion disease were among those with the largest electrostatic energies. The large barrier to charged group desolvation imposes regional constraints on involvement of the prion protein in an amyloid aggregate, resulting in an electrostatic amyloid recruitment profile that favours regions of sequence between α helix 1 and β strand 2, the middles of helices 2 and 3, and the region N-terminal to α helix 1. We found that the stabilization due to salt bridges is minimal among the proteins studied for disease-susceptible human mutants of prion protein.

scholarly journals Intra-helical salt bridge contribution to membrane protein insertion

2021 ◽  
Author(s):  
Gerard Duart ◽  
John Lamb ◽  
Arne Elofsson ◽  
Ismael Mingarro
Keyword(s):  
Amino Acids ◽  
Membrane Protein ◽  
Electrostatic Interactions ◽  
Salt Bridge ◽  
Protein Stabilization ◽  
Membrane Insertion ◽  
Salt Bridges ◽  
Protein Insertion

ABSTRACTSalt bridges between negatively (D, E) and positively charged (K, R, H) amino acids play an important role in protein stabilization. This has a more prevalent effect in membrane proteins where polar amino acids are exposed to a very hydrophobic environment. In transmembrane (TM) helices the presence of charged residues can hinder the insertion of the helices into the membrane. This can sometimes be avoided by TM region rearrangements after insertion, but it is also possible that the formation of salt bridges could decrease the cost of membrane integration. However, the presence of intra-helical salt bridges in TM domains and their effect on insertion has not been properly studied yet. In this work, we use an analytical pipeline to study the prevalence of charged pairs of amino acid residues in TM α-helices, which shows that potentially salt-bridge forming pairs are statistically over-represented. We then selected some candidates to experimentally determine the contribution of these electrostatic interactions to the translocon-assisted membrane insertion process. Using both in vitro and in vivo systems, we confirm the presence of intra-helical salt bridges in TM segments during biogenesis and determined that they contribute between 0.5-0.7 kcal/mol to the apparent free energy of membrane insertion (ΔGapp). Our observations suggest that salt bridge interactions can be stabilized during translocon-mediated insertion and thus could be relevant to consider for the future development of membrane protein prediction software.

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