Type II transmembrane domain hydrophobicity dictates the cotranslational dependence for inversion

Membrane insertion by the Sec61 translocon in the endoplasmic reticulum (ER) is highly dependent on hydrophobicity. This places stringent hydrophobicity requirements on transmembrane domains (TMDs) from single-spanning membrane proteins. On examining the single-spanning influenza A membrane proteins, we found that the strict hydrophobicity requirement applies to the Nout-CinHA and M2 TMDs but not the Nin-CoutTMDs from the type II membrane protein neuraminidase (NA). To investigate this discrepancy, we analyzed NA TMDs of varying hydrophobicity, followed by increasing polypeptide lengths, in mammalian cells and ER microsomes. Our results show that the marginally hydrophobic NA TMDs (ΔGapp> 0 kcal/mol) require the cotranslational insertion process for facilitating their inversion during translocation and a positively charged N-terminal flanking residue and that NA inversion enhances its plasma membrane localization. Overall the cotranslational inversion of marginally hydrophobic NA TMDs initiates once ∼70 amino acids past the TMD are synthesized, and the efficiency reaches 50% by ∼100 amino acids, consistent with the positioning of this TMD class in type II human membrane proteins. Inversion of the M2 TMD, achieved by elongating its C-terminus, underscores the contribution of cotranslational synthesis to TMD inversion.

Download Full-text

Distinct Requirements for Tail-Anchored Membrane Protein Biogenesis in Escherichia coli

mBio ◽

10.1128/mbio.01580-19 ◽

2019 ◽

Vol 10 (5) ◽

Cited By ~ 1

Author(s):

Markus Peschke ◽

Mélanie Le Goff ◽

Gregory M. Koningstein ◽

Norbert O. Vischer ◽

Abbi Abdel-Rehim ◽

...

Keyword(s):

Escherichia Coli ◽

Membrane Proteins ◽

Transmembrane Domain ◽

Signal Recognition Particle ◽

Membrane Insertion ◽

Type Ii ◽

Content Type ◽

E Coli ◽

C Terminus

ABSTRACT Tail-anchored membrane proteins (TAMPs) are a distinct subset of inner membrane proteins (IMPs) characterized by a single C-terminal transmembrane domain (TMD) that is responsible for both targeting and anchoring. Little is known about the routing of TAMPs in bacteria. Here, we have investigated the role of TMD hydrophobicity in tail-anchor function in Escherichia coli and its influence on the choice of targeting/insertion pathway. We created a set of synthetic, fluorescent TAMPs that vary in the hydrophobicity of their TMDs and corresponding control polypeptides that are extended at their C terminus to create regular type II IMPs. Surprisingly, we observed that TAMPs have a much lower TMD hydrophobicity threshold for efficient targeting and membrane insertion than their type II counterparts. Using strains conditional for the expression of known membrane-targeting and insertion factors, we show that TAMPs with strongly hydrophobic TMDs require the signal recognition particle (SRP) for targeting. Neither the SecYEG translocon nor YidC appears to be essential for the membrane insertion of any of the TAMPs studied. In contrast, corresponding type II IMPs with a TMD of sufficient hydrophobicity to promote membrane insertion followed an SRP- and SecYEG translocon-dependent pathway. Together, these data indicate that the capacity of a TMD to promote the biogenesis of E. coli IMPs is strongly dependent upon the polypeptide context in which it is presented. IMPORTANCE A subset of membrane proteins is targeted to and inserted into the membrane via a hydrophobic transmembrane domain (TMD) that is positioned at the very C terminus of the protein. The biogenesis of these so-called tail-anchored proteins (TAMPs) has been studied in detail in eukaryotic cells. Various partly redundant pathways were identified, the choice for which depends in part on the hydrophobicity of the TMD. Much less is known about bacterial TAMPs. The significance of our research is in identifying the role of TMD hydrophobicity in the routing of E. coli TAMPs. Our data suggest that both the nature of the TMD and its role in routing can be very different for TAMPs versus “regular” membrane proteins. Elucidating these position-specific effects of TMDs will increase our understanding of how prokaryotic cells face the challenge of producing a wide variety of membrane proteins.

Download Full-text

Role of Transmembrane Domain and Cytoplasmic Tail Amino Acid Sequences of Influenza A Virus Neuraminidase in Raft Association and Virus Budding

Journal of Virology ◽

10.1128/jvi.78.10.5258-5269.2004 ◽

2004 ◽

Vol 78 (10) ◽

pp. 5258-5269 ◽

Cited By ~ 80

Author(s):

Subrata Barman ◽

Lopa Adhikary ◽

Alok K. Chakrabarti ◽

Carl Bernas ◽

Yoshihiro Kawaoka ◽

...

Keyword(s):

Amino Acids ◽

Amino Acid ◽

Influenza A ◽

Transmembrane Domain ◽

Amino Acid Sequences ◽

Type Ii ◽

Virus Growth ◽

Transmembrane Glycoprotein ◽

Virus Life Cycle

ABSTRACT Influenza virus neuraminidase (NA), a type II transmembrane glycoprotein, possesses receptor-destroying activity and thereby facilitates virus release from the cell surface. Among the influenza A viruses, both the cytoplasmic tail (CT) and transmembrane domain (TMD) amino acid sequences of NA are highly conserved, yet their function(s) in virus biology remains unknown. To investigate the role of amino acid sequences of the CT and TMD on the virus life cycle, we systematically mutagenized the entire CT and TMD of NA by converting two to five contiguous amino acids to alanine. In addition, we also made two chimeric NA by replacing the CT proximal one-third amino acids of the NA TMD [NA(1T2N)NA] and the entire NA TMD (NATRNA) with that of human transferrin receptor (TR) (a type II transmembrane glycoprotein). We rescued transfectant mutant viruses by reverse genetics and examined their phenotypes. Our results show that all mutated and chimeric NAs could be rescued into transfectant viruses. Different mutants showed pleiotropic effects on virus growth and replication. Some mutants (NA2A5, NA3A7, and NA4A10) had little effect on virus growth while others (NA3A2, NA5A27, and NA5A31) produced about 50- to 100-fold-less infectious virus and still some others (NA5A14, NA4A19, and NA4A23) exhibited an intermediate phenotype. In general, mutations towards the ectodomain-proximal sequences of TMD progressively caused reduction in NA enzyme activity, affected lipid raft association, and attenuated virus growth. Electron microscopic analysis showed that these mutant viruses remained aggregated and bound to infected cell surfaces and could be released from the infected cells by bacterial NA treatment. Moreover, viruses containing mutations in the extreme N terminus of the CT (NA3A2) as well as chimeric NA containing the TMD replaced partially [NA(1T2N)NA] or fully (NATRNA) with TR TMD caused reduction in virus growth and exhibited the morphological phenotype of elongated particles. These results show that although the sequences of NA CT and TMD per se are not absolutely essential for the virus life cycle, specific amino acid sequences play a critical role in providing structural stability, enzyme activity, and lipid raft association of NA. In addition, aberrant morphogenesis including elongated particle formation of some mutant viruses indicates the involvement of NA in virus morphogenesis and budding.

Download Full-text

Regulation of Bestrophin Cl Channels by Calcium: Role of the C Terminus

The Journal of General Physiology ◽

10.1085/jgp.200810056 ◽

2008 ◽

Vol 132 (6) ◽

pp. 681-692 ◽

Cited By ~ 54

Author(s):

Qinghuan Xiao ◽

Andrew Prussia ◽

Kuai Yu ◽

Yuan-yuan Cui ◽

H. Criss Hartzell

Keyword(s):

Amino Acids ◽

Density Functional ◽

Transmembrane Domain ◽

Channel Gating ◽

Regulatory Domain ◽

Acidic Amino Acids ◽

C Terminus ◽

Ef Hand ◽

Cl Channels

Human bestrophin-1 (hBest1), which is genetically linked to several kinds of retinopathy and macular degeneration in both humans and dogs, is the founding member of a family of Cl− ion channels that are activated by intracellular Ca2+. At present, the structures and mechanisms responsible for Ca2+ sensing remain unknown. Here, we have used a combination of molecular modeling, density functional–binding energy calculations, mutagenesis, and patch clamp to identify the regions of hBest1 involved in Ca2+ sensing. We identified a cluster of a five contiguous acidic amino acids in the C terminus immediately after the last transmembrane domain, followed by an EF hand and another regulatory domain that are essential for Ca2+ sensing by hBest1. The cluster of five amino acids (293–308) is crucial for normal channel gating by Ca2+ because all but two of the 35 mutations we made in this region rendered the channel incapable of being activated by Ca2+. Using homology models built on the crystal structure of calmodulin (CaM), an EF hand (EF1) was identified in hBest1. EF1 was predicted to bind Ca2+ with a slightly higher affinity than the third EF hand of CaM and lower affinity than the second EF hand of troponin C. As predicted by the model, the D312G mutation in the putative Ca2+-binding loop (312–323) reduced the apparent Ca2+ affinity by 20-fold. In addition, the D312G and D323N mutations abolished Ca2+-dependent rundown of the current. Furthermore, analysis of truncation mutants of hBest1 identified a domain adjacent to EF1 that is rich in acidic amino acids (350–390) that is required for Ca2+ activation and plays a role in current rundown. These experiments identify a region of hBest1 (312–323) that is involved in the gating of hBest1 by Ca2+ and suggest a model in which Ca2+ binding to EF1 activates the channel in a process that requires the acidic domain (293–308) and another regulatory domain (350–390). Many of the ∼100 disease-causing mutations in hBest1 are located in this region that we have implicated in Ca2+ sensing, suggesting that these mutations disrupt hBest1 channel gating by Ca2+.

Download Full-text

Localization of Functional Domains of the Mitogenic Toxin of Pasteurella multocida

Infection and Immunity ◽

10.1128/iai.69.12.7839-7850.2001 ◽

2001 ◽

Vol 69 (12) ◽

pp. 7839-7850 ◽

Cited By ~ 39

Author(s):

Gillian D. Pullinger ◽

R. Sowdhamini ◽

Alistair J. Lax

Keyword(s):

Amino Acids ◽

Fusion Proteins ◽

Pasteurella Multocida ◽

Transmembrane Domain ◽

Polyclonal Antibodies ◽

Full Length ◽

Cell Binding ◽

Terminal Fragment ◽

C Terminus ◽

N Terminus

ABSTRACT The locations of the catalytic and receptor-binding domains of thePasteurella multocida toxin (PMT) were investigated. N- and C-terminal fragments of PMT were cloned and expressed as fusion proteins with affinity tags. Purified fusion proteins were assessed in suitable assays for catalytic activity and cell-binding ability. A C-terminal fragment (amino acids 681 to 1285) was catalytically active. When microinjected into quiescent Swiss 3T3 cells, it induced changes in cell morphology typical of toxin-treated cells and stimulated DNA synthesis. An N-terminal fragment with a His tag at the C terminus (amino acids 1 to 506) competed with full-length toxin for binding to surface receptors and therefore contains the cell-binding domain. The inactive mutant containing a mutation near the C terminus (C1165S) also bound to cells in this assay. Polyclonal antibodies raised to the N-terminal PMT region bound efficiently to full-length native toxin, suggesting that the N terminus is surface located. Antibodies to the C terminus of PMT were microinjected into cells and inhibited the activity of toxin added subsequently to the medium, confirming that the C terminus contains the active site. Analysis of the PMT sequence predicted a putative transmembrane domain with predicted hydrophobic and amphipathic helices near the N terminus over the region of homology to the cytotoxic necrotizing factors. The C-terminal end of PMT was predicted to be a mixed α/β domain, a structure commonly found in catalytic domains. Homology to proteins of known structure and threading calculations supported these assignments.

Download Full-text

MISTERMINATE Mechanistically Links Mitochondrial Dysfunction with Proteostasis Failure

10.1101/554634 ◽

2019 ◽

Cited By ~ 1

Author(s):

Zhihao Wu ◽

Ishaq Tantray ◽

Junghyun Lim ◽

Songjie Chen ◽

Yu Li ◽

...

Keyword(s):

Amino Acids ◽

Mitochondrial Dysfunction ◽

Complex I ◽

Mammalian Cells ◽

Protein C ◽

Stop Codon ◽

Translation Termination ◽

Disease Model ◽

C Terminus ◽

Translational Termination

SUMMARYMitochondrial dysfunction and proteostasis failure frequently coexist as hallmarks of neurodegenerative disease. How these pathologies are related is not well understood. Here we describe a phenomenon termed MISTERMINATE (mitochondrial stress-induced translational termination impairment and protein carboxyl terminal extension), which mechanistically links mitochondrial dysfunction with proteostasis failure. We show that mitochondrial dysfunction impairs translational termination of nuclear-encoded mitochondrial mRNAs including complex-I 30kD subunit (C-I30) mRNA, occurring on mitochondrial surface in Drosophila and mammalian cells. Ribosomes stalled at the normal stop codon continue to add to the C-terminus of C-I30 certain amino acids non-coded by mRNA template. C-terminally-extended C-I30 is toxic when assembled into C-I and forms aggregates in the cytosol. Enhancing co-translational quality control prevents C-I30 C-terminal extension and rescues mitochondrial and neuromuscular degeneration in a Parkinson’s disease model. These findings emphasize the importance of efficient translation termination and reveal unexpected link between mitochondrial health and proteome homeostasis mediated by MISTERMINATE.

Download Full-text

Unique Light-gated Ion Channel Properties of a Novel Modular Cation Channelrhodopsin from an Evolutionary Important Terrestrial Green Alga

10.21203/rs.3.rs-68371/v1 ◽

2020 ◽

Author(s):

Rintaro Tashiro ◽

Kumari Sushmita ◽

Shoko Hososhima ◽

Sunita Sharma ◽

Suneel Kateriya ◽

...

Keyword(s):

Ion Channel ◽

Mammalian Cells ◽

Transmembrane Domain ◽

Action Spectrum ◽

Closure Rate ◽

C Terminus ◽

Ion Channel Properties ◽

Arginine Residues ◽

Tm Domain ◽

Channel Currents

Abstract Channelrhodopsins are a family of microbial rhodopsins that function as a light-gated ion channel. We report the molecular properties of a novel channelrhodopsin KnRh3 from an evolutionary important filamentous terrestrial alga Klebsormidium nitens. KnRh3 is constituted of a 7-transmembrane domain, followed by a long C-terminus moiety that encodes a peptidoglycan binding domain (FimV). When functionally expressed in mammalian cells, KnRh3 showed light-induced cation channel currents. The maximum action spectrum exhibited was at 430 nm and 460 nm, the former making KnRh3 one of the most blue-shifted channelrhodopsins characterized thus far. The channel closure rate was relatively fast (τ0ff = 10 ms). Surprisingly, photocurrent kinetics were affected by the C-terminus moiety of KnRh3. When this moiety was truncated to various lengths, this prolonged the channel open lifetime by more than 10-fold. We identified two arginine residues, R287 and R291, those are crucial for altering the kinetics. We propose that electrostatic interaction between the 7-TM domain and the C-terminus domain accelerates the photocycle. The most blue-shifted action spectrum of KnRh3 serves as a novel prototype of channelrhodopsin for studying the molecular mechanism of color tuning. In addition, KnRh3 would expand the optogenetics tool kit, especially for when short wavelength excitation is required.

Download Full-text

The Vaccinia Virus 14-Kilodalton (A27L) Fusion Protein Forms a Triple Coiled-Coil Structure and Interacts with the 21-Kilodalton (A17L) Virus Membrane Protein through a C-Terminal α-Helix

Journal of Virology ◽

10.1128/jvi.72.12.10126-10137.1998 ◽

1998 ◽

Vol 72 (12) ◽

pp. 10126-10137 ◽

Cited By ~ 44

Author(s):

María-Isabel Vázquez ◽

German Rivas ◽

David Cregut ◽

Luis Serrano ◽

Mariano Esteban

Keyword(s):

Amino Acids ◽

Vaccinia Virus ◽

Structural Model ◽

Analytical Ultracentrifugation ◽

Transmembrane Domain ◽

Coiled Coil ◽

C Terminus ◽

Α Helix ◽

Mutant Forms ◽

Helical Region

ABSTRACT The vaccinia virus 14-kDa protein (encoded by the A27L gene) plays an important role in the biology of the virus, acting in virus-to-cell and cell-to-cell fusions. The protein is located on the surface of the intracellular mature virus form and is essential for both the release of extracellular enveloped virus from the cells and virus spread. Sequence analysis predicts the existence of four regions in this protein: a structureless region from amino acids 1 to 28, a helical region from residues 29 to 37, a triple coiled-coil helical region from residues 44 to 72, and a Leu zipper motif at the C terminus. Circular dichroism spectroscopy, analytical ultracentrifugation, and chemical cross-linking studies of the purified wild-type protein and several mutant forms, lacking one or more of the above regions or with point mutations, support the above-described structural division of the 14-kDa protein. The two contiguous cysteine residues at positions 71 and 72 are not responsible for the formation of 14-kDa protein trimers. The location of hydrophobic residues at the a and d positions on a helical wheel and of charged amino acids in adjacent positions, e and g, suggests that the hydrophobic and ionic interactions in the triple coiled-coil helical region are involved in oligomer formation. This conjecture was supported by the construction of a three-helix bundle model and molecular dynamics. Binding assays with purified proteins expressed in Escherichia coli and cytoplasmic extracts from cells infected with a virus that does not produce the 14-kDa protein during infection (VVindA27L) show that the 21-kDa protein (encoded by the A17L gene) is the specific viral binding partner and identify the putative Leu zipper, the predicted third α-helix on the C terminus of the 14-kDa protein, as the region involved in protein binding. These findings were confirmed in vivo, following transfection of animal cells with plasmid vectors expressing mutant forms of the 14-kDa protein and infected with VVindA27L. We find the structural organization of 14kDa to be similar to that of other fusion proteins, such as hemagglutinin of influenza virus and gp41 of human immunodeficiency virus, except for the presence of a protein-anchoring domain instead of a transmembrane domain. Based on our observations, we have established a structural model of the 14-kDa protein.

Download Full-text

Evidence for a Holin-Like Protein Gene Fully Embedded Out of Frame in the Endolysin Gene of Staphylococcus aureusBacteriophage 187

Journal of Bacteriology ◽

10.1128/jb.181.15.4452-4460.1999 ◽

1999 ◽

Vol 181 (15) ◽

pp. 4452-4460 ◽

Cited By ~ 57

Author(s):

Martin J. Loessner ◽

Susanne Gaeng ◽

Siegfried Scherer

Keyword(s):

Amino Acids ◽

Cytoplasmic Membrane ◽

Transmembrane Domain ◽

De Novo ◽

Atp Synthesis ◽

Large Cell ◽

Lytic Enzyme ◽

Reading Frame ◽

C Terminus

ABSTRACT We have cloned, sequenced, and characterized the genes encoding the lytic system of the unique Staphylococcus aureus phage 187. The endolysin gene ply187 encodes a large cell wall-lytic enzyme (71.6 kDa). The catalytic site, responsible for the hydrolysis of staphylococcal peptidoglycan, was mapped to the N-terminal domain of the protein by the expression of defined ply187 domains. This enzymatically active N terminus showed convincing amino acid sequence homology to anN-acetylmuramoyl-l-alanine amidase, whereas the C-terminal part, whose function is unknown, revealed striking relatedness to major staphylococcal autolysins. An additional reading frame was identified entirely embedded out of frame (+1) within the 5′ region of ply187 and was shown to encode a small, hydrophobic protein of holin-like function. The hol187 gene features a dual-start motif, possibly enabling the synthesis of two products of different lengths (57 and 55 amino acids, respectively). Overproduction of Hol187 in Escherichia coli resulted in growth retardation, leakiness of the cytoplasmic membrane, and loss of de novo ATP synthesis. Compared to other holins identified to date, Hol187 completely lacks the highly charged C terminus. The secondary structure of the polypeptide is predicted to consist of two small, antiparallel, hydrophobic, transmembrane helices. These are supposed to be essential for integration into the membrane, since site-specific introduction of negatively charged amino acids into the first transmembrane domain (V7D G8D) completely abolished the function of the Hol187 polypeptide. With antibodies raised against a synthetic 18-mer peptide representing a central part of the protein, it was possible to detect Hol187 in the cytoplasmic membrane of phage-infected S. aureus cells. An important indication that the protein actually functions as a holin in vivo was that the gene (but not the V7D G8D mutation) was able to complement a phage λ Sam mutation in a nonsuppressing E. coli HB101 background. Plaque formation by λgt11::hol187 indicated that both phage genes have analogous functions. The data presented here indicate that a putative holin is encoded on a different reading frame within the enzymatically active domain of ply187 and that the holin is synthesized during the late stage of phage infection and found in the cytoplasmic membrane, where it causes membrane lesions which are thought to enable access of Ply187 to the peptidoglycan of phage-infected Staphylococcus cells.

Download Full-text

Molecular determinants of activation and membrane targeting of phosphoinositol 4-kinase IIβ

Biochemical Journal ◽

10.1042/bj20070821 ◽

2007 ◽

Vol 409 (2) ◽

pp. 501-509 ◽

Cited By ~ 29

Author(s):

Gwanghyun Jung ◽

Jing Wang ◽

Pawel Wlodarski ◽

Barbara Barylko ◽

Derk D. Binns ◽

...

Keyword(s):

Mammalian Cells ◽

Kinase Activity ◽

Catalytic Domain ◽

Transmembrane Domain ◽

Integral Membrane Protein ◽

Type Ii ◽

Lipid Kinase ◽

Catalytic Domains ◽

Specific Behaviour ◽

Molecular Determinants

Mammalian cells contain two isoforms of the type II PI4K (phosphoinositol 4-kinase), PI4KIIα and β. These 55 kDa proteins have highly diverse N-terminal regions (approximately residues 1–90) but conserved catalytic domains (approximately from residue 91 to the C-termini). Nearly the entire pool of PI4KIIα behaves as an integral membrane protein, in spite of a lack of a transmembrane domain. This integral association with membranes is due to palmitoylation of a cysteine-rich motif, CCPCC, located within the catalytic domain. Although the CCPCC motif is conserved in PI4KIIβ, only 50% of PI4KIIβ is membrane-associated, and approximately half of this pool is only peripherally attached to the membranes. Growth factor stimulation or overexpression of a constitutively active Rac mutant induces the translocation of a portion of cytosolic PI4KIIβ to plasma membrane ruffles and stimulates its activity. Here, we demonstrate that membrane-associated PI4KIIβ undergoes two modifications, palmitoylation and phosphorylation. The cytosolic pool of PI4KIIβ is not palmitoylated and has much lower lipid kinase activity than the membrane-associated kinase. Although only membrane-associated PI4KIIβ is phosphorylated in the unique N-terminal region, this modification apparently does not influence its membrane binding or activity. A series of truncation mutants and α/β chimaeras were generated to identify regions responsible for the isoform-specific behaviour of the kinases. Surprisingly, the C-terminal approx. 160 residues, and not the diverse N-terminal regions, contain the sites that are most important in determining the different solubilities, palmitoylation states and stimulus-dependent redistributions of PI4KIIα and β.

Download Full-text

Arginine mutations within a transmembrane domain of Tar, an Escherichia coli aspartate receptor, can drive homodimer dissociation and heterodimer association in vivo

Biochemical Journal ◽

10.1042/bj20041022 ◽

2004 ◽

Vol 385 (1) ◽

pp. 29-36 ◽

Cited By ~ 11

Author(s):

Neta SAL-MAN ◽

Yechiel SHAI

Keyword(s):

Amino Acids ◽

Transmembrane Domain ◽

Genetic Diseases ◽

Ion Pairs ◽

Aspartate Receptor ◽

Charged Residues ◽

Arginine Residues ◽

Tm Domain ◽

Positively Charged

The interactions between the TM (transmembrane) domains of many membrane proteins are important for their proper functioning. Mutations of residues into positively charged ones within TM domains were reported to be involved in many genetic diseases, possibly because these mutations affect the self- and/or hetero-assembly of the corresponding proteins. To our knowledge, despite significant progress in understanding the role of various amino acids in TM–TM interactions in vivo, the direct effect of positively charged residues on these interactions has not been studied. To address this issue, we employed the N-terminal TM domain of the aspartate receptor (Tar-1) as a dimerization model system. We expressed within the ToxR TM assembly system several Tar-1 constructs that dimerize via polar- or non-polar amino acid motifs, and mutated these by replacement with a single arginine residue. Our results have revealed that a mutation in each of the motifs significantly reduced the ability of the TMs to dimerize. Furthermore, a Tar-1 construct that contained two arginine residues was unable to correctly integrate itself into the membrane. Nevertheless, an exogenous synthetic Tar-1 peptide containing these two arginine residues was able to inhibit in vivo the marked dimerization of a mutant Tar-1 construct that contained two glutamate residues at similar positions. This indicates that hetero-assembly of TM domains can be mediated by the interaction of two oppositely charged residues, probably by formation of ion pairs. This study broadens our knowledge regarding the effect of positively charged residues on TM–TM interactions in vivo, and provides a potential therapeutic approach to inhibit uncontrolled dimerization of TM domains caused by mutations of polar amino acids.

Download Full-text