scholarly journals Inactivation of erythropoietin receptor function by point mutations in a region having homology with other cytokine receptors.

1993 ◽  
Vol 13 (3) ◽  
pp. 1788-1795 ◽  
Author(s):  
O Miura ◽  
J L Cleveland ◽  
J N Ihle
Keyword(s):  
Amino Acid ◽  
Tyrosine Phosphorylation ◽  
Transmembrane Domain ◽  
Point Mutations ◽  
Cell Receptor ◽  
Erythropoietin Receptor ◽  
Immediate Early ◽  
Amino Acid Residues ◽  
Dependent Cell ◽  
Critical Residues

The cytoplasmic domain of the erythropoietin receptor (EpoR) contains a region, proximal to the transmembrane domain, that is essential for function and has homology with other members of the cytokine receptor family. To explore the functional significance of this region and to identify critical residues, we introduced several amino acid substitutions and examined their effects on erythropoietin-induced mitogenesis, tyrosine phosphorylation, and expression of immediate-early (c-fos, c-myc, and egr-1) and early (ornithine decarboxylase and T-cell receptor gamma) genes in interleukin-3-dependent cell lines. Amino acid substitution of W-282, which is strictly conserved at the middle portion of the homology region, completely abolished all the functions of the EpoR. Point mutation at L-306 or E-307, both of which are in a conserved LEVL motif, drastically impaired the function of the receptor in all assays. Other point mutations, introduced into less conserved amino acid residues, did not significantly impair the function of the receptor. These results demonstrate that conserved amino acid residues in this domain of the EpoR are required for mitogenesis, stimulation of tyrosine phosphorylation, and induction of immediate-early and early genes.

Inactivation of erythropoietin receptor function by point mutations in a region having homology with other cytokine receptors

1993 ◽  
Vol 13 (3) ◽  
pp. 1788-1795
Author(s):  
O Miura ◽  
J L Cleveland ◽  
J N Ihle
Keyword(s):  
Amino Acid ◽  
Tyrosine Phosphorylation ◽  
Transmembrane Domain ◽  
Point Mutations ◽  
Cell Receptor ◽  
Erythropoietin Receptor ◽  
Immediate Early ◽  
Amino Acid Residues ◽  
Dependent Cell ◽  
Critical Residues

The cytoplasmic domain of the erythropoietin receptor (EpoR) contains a region, proximal to the transmembrane domain, that is essential for function and has homology with other members of the cytokine receptor family. To explore the functional significance of this region and to identify critical residues, we introduced several amino acid substitutions and examined their effects on erythropoietin-induced mitogenesis, tyrosine phosphorylation, and expression of immediate-early (c-fos, c-myc, and egr-1) and early (ornithine decarboxylase and T-cell receptor gamma) genes in interleukin-3-dependent cell lines. Amino acid substitution of W-282, which is strictly conserved at the middle portion of the homology region, completely abolished all the functions of the EpoR. Point mutation at L-306 or E-307, both of which are in a conserved LEVL motif, drastically impaired the function of the receptor in all assays. Other point mutations, introduced into less conserved amino acid residues, did not significantly impair the function of the receptor. These results demonstrate that conserved amino acid residues in this domain of the EpoR are required for mitogenesis, stimulation of tyrosine phosphorylation, and induction of immediate-early and early genes.

scholarly journals Comparative ACE2 variation and primate COVID-19 risk

2020 ◽  
Vol 3 (1) ◽  
Author(s):  
Amanda D. Melin ◽  
Mareike C. Janiak ◽  
Frank Marrone ◽  
Paramjit S. Arora ◽  
James P. Higham
Keyword(s):  
Amino Acid ◽  
Nonhuman Primates ◽  
Cell Receptor ◽  
Primate Species ◽  
Amino Acid Residues ◽  
Host Cell Receptor ◽  
Infection Susceptibility ◽  
Contact Residues ◽  
Critical Residues ◽  
Critical Contact

Abstract The emergence of SARS-CoV-2 has caused over a million human deaths and massive global disruption. The viral infection may also represent a threat to our closest living relatives, nonhuman primates. The contact surface of the host cell receptor, ACE2, displays amino acid residues that are critical for virus recognition, and variations at these critical residues modulate infection susceptibility. Infection studies have shown that some primate species develop COVID-19-like symptoms; however, the susceptibility of most primates is unknown. Here, we show that all apes and African and Asian monkeys (catarrhines), exhibit the same set of twelve key amino acid residues as human ACE2. Monkeys in the Americas, and some tarsiers, lemurs and lorisoids, differ at critical contact residues, and protein modeling predicts that these differences should greatly reduce SARS-CoV-2 binding affinity. Other lemurs are predicted to be closer to catarrhines in their susceptibility. Our study suggests that apes and African and Asian monkeys, and some lemurs, are likely to be highly susceptible to SARS-CoV-2. Urgent actions have been undertaken to limit the exposure of great apes to humans, and similar efforts may be necessary for many other primate species.

Saturation Mutagenesis of the β Subunit of the Human Granulocyte-Macrophage Colony-Stimulating Factor Receptor Shows Clustering of Constitutive Mutations, Activation of ERK MAP Kinase and STAT Pathways, and Differential β Subunit Tyrosine Phosphorylation

Blood ◽  
1998 ◽  
Vol 92 (6) ◽  
pp. 1989-2002 ◽  
Author(s):  
Brendan J. Jenkins ◽  
Timothy J. Blake ◽  
Thomas J. Gonda
Keyword(s):  
Map Kinase ◽  
Tyrosine Phosphorylation ◽  
Transmembrane Domain ◽  
Point Mutations ◽  
Saturation Mutagenesis ◽  
Β Subunit ◽  
Colony Stimulating Factor ◽  
Macrophage Colony Stimulating Factor ◽  
Macrophage Colony ◽  
Stimulating Factor

Abstract The high-affinity receptors for human granulocyte-macrophage colony-stimulating factor (GM-CSF), interleukin-3 (IL-3), and IL-5 are heterodimeric complexes consisting of cytokine-specific  subunits and a common signal-transducing β subunit (hβc). We have previously demonstrated the oncogenic potential of this group of receptors by identifying constitutively activating point mutations in the extracellular and transmembrane domains of hβc. We report here a comprehensive screen of the entire hβc molecule that has led to the identification of additional constitutive point mutations by virtue of their ability to confer factor independence on murine FDC-P1 cells. These mutations were clustered exclusively in a central region of hβc that encompasses the extracellular membrane-proximal domain, transmembrane domain, and membrane-proximal region of the cytoplasmic domain. Interestingly, most hβc mutants exhibited cell type-specific constitutive activity, with only two transmembrane domain mutants able to confer factor independence on both murine FDC-P1 and BAF-B03 cells. Examination of the biochemical properties of these mutants in FDC-P1 cells indicated that MAP kinase (ERK1/2), STAT, and JAK2 signaling molecules were constitutively activated. In contrast, only some of the mutant β subunits were constitutively tyrosine phosphorylated. Taken together, these results highlight key regions involved in hβc activation, dissociate hβc tyrosine phosphorylation from MAP kinase and STAT activation, and suggest the involvement of distinct mechanisms by which proliferative signals can be generated by hβc. © 1998 by The American Society of Hematology.

scholarly journals Activation of Ha-ras p21 by substitution, deletion, and insertion mutations.

1985 ◽  
Vol 5 (8) ◽  
pp. 1809-1813 ◽  
Author(s):  
R G Chipperfield ◽  
S S Jones ◽  
K M Lo ◽  
R A Weinberg
Keyword(s):  
Amino Acid ◽  
Point Mutations ◽  
Normal Function ◽  
Site Directed Mutagenesis ◽  
Directed Mutagenesis ◽  
Amino Acid Residues ◽  
Transforming Activity ◽  
Ras P21 ◽  
Ras Oncogenes ◽  
Insertion Mutations

The transforming activity of naturally arising ras oncogenes results from point mutations that affect residue 12 or 61 of the encoded 21-kilodalton protein (p21). By use of site-directed mutagenesis, we showed that deletions and insertions of amino acid residues in the region of residue 12 are also effective in conferring oncogenic activity on p21. Common to these various alterations is the disruption that they create in this domain of the protein, which we propose results in the inactivation of a normal function of the protein.

scholarly journals PC8 [corrected], a new member of the convertase family

1996 ◽  
Vol 314 (3) ◽  
pp. 727-731 ◽  
Author(s):  
Angela BRUZZANITI ◽  
Katrina GOODGE ◽  
Philippe JAY ◽  
Sylvie A. TAVIAUX ◽  
Mark H. C. Lam ◽  
...  
Keyword(s):  
Amino Acid ◽  
Transmembrane Domain ◽  
Duplication Event ◽  
Amino Acid Identity ◽  
Chromosome 15 ◽  
Rat Tissues ◽  
Amino Acid Residues ◽  
Degenerate Primers ◽  
Chromosome 11Q23 ◽  
Ancient Gene Duplication

A novel subtilisin-like protein, PC8, was identified by PCR using degenerate primers to conserved amino acid residues in the catalytic region of members of the prohormone convertase family. PC8 was predicted to be 785 residues long and was structurally related to the mammalian convertases furin, PACE4, PC1 and PC2, sharing more than 50% amino acid identity over the catalytic region with these family members. PC8 possessed the catalytically important Asp, His, Asn and Ser amino acids, the homo B domain of this family of enzymes and a C-terminal hydrophobic sequence indicative of a transmembrane domain. Structurally, PC8 is more related to furin and PACE4 than to PC1 or PC2. Like furin and PACE4, PC8 mRNA was found to be widely expressed; this is in contrast with PC1 and PC2, which have a restricted distribution. Two transcripts, of 4.5 and 3.5 kb, were detected in both human cell lines and rat tissues. Unlike furin and PACE4, both of which map to chromosome 15, PC8 maps to chromosome 11q23–11q24, suggesting that this gene may have resulted from an ancient gene duplication event from either furin or PACE4, or conversely that these genes arose from PC8.

scholarly journals The Integrin β1 Subunit Transmembrane Domain Regulates Phosphatidylinositol 3-Kinase-dependent Tyrosine Phosphorylation of Crk-associated Substrate

2004 ◽  
Vol 15 (6) ◽  
pp. 2558-2567 ◽  
Author(s):  
Annika Armulik ◽  
Teet Velling ◽  
Staffan Johansson
Keyword(s):  
Amino Acid ◽  
Tyrosine Phosphorylation ◽  
Transmembrane Domain ◽  
Basic Amino Acid ◽  
Proximal Part ◽  
Phosphatidylinositol 3 Kinase ◽  
Integrin Β1 ◽  
Downstream Target ◽  
Mediate Cell ◽  
Phosphatidylinositol 3

Our previous studies on the transmembrane domain of human integrin subunits have shown that a conserved basic amino acid in both subunits of integrin heterodimers is positioned in the plasma membrane in the absence of interacting proteins. To investigate the possible functional role of the lipid-embedded lysine in the mouse integrin β1 subunit, this amino acid was replaced with leucine, and the mutated β1 subunit (β1AK756L) was stably expressed in β1-deficient GD25 cells. The extracellular domain of β1AK756L integrins possesses a competent conformation for ligand binding as determined by the ability to mediate cell adhesion, and by the presence of the monoclonal antibody 9EG7 epitope. However, the spreading of GD25-β1AK756L cells on fibronectin and laminin-1 was impaired, and the rate of migration of GD25-β1AK756L cells on fibronectin was reduced compared with GD25-β1A cells. Phosphorylation of tyrosines in focal adhesion kinase (FAK) and the Y416 in c-Src in response to β1AK756L-mediated adhesion was similar to that induced by wild-type β1. The tyrosine phosphorylation level of paxillin, a downstream target of FAK/Src, was unaffected by the β1 mutation, whereas tyrosine phosphorylation of CAS was strongly reduced. The results demonstrate that CAS is a target for phosphorylation both by FAK-dependent and -independent pathways after integrin ligation. The latter pathway was inhibited by wortmannin and LY294002, implicating that it required an active phosphatidylinositol 3-kinase. Furthermore, the K756L mutation in the β1 subunit was found to interfere with β1-induced activation of Akt. The results from this study identify phosphatidylinositol 3-kinase as an early component of a FAK-independent integrin signaling pathway triggered by the membrane proximal part of the β1 subunit.

scholarly journals Mefloquine and New Related Compounds Target the F0 Complex of the F0F1 H+-ATPase of Streptococcus pneumoniae

2002 ◽  
Vol 46 (6) ◽  
pp. 1680-1687 ◽  
Author(s):  
Antonio Javier Martín-Galiano ◽  
Begoña Gorgojo ◽  
Calvin M. Kunin ◽  
Adela G. de la Campa
Keyword(s):  
Streptococcus Pneumoniae ◽  
Amino Acid ◽  
Proton Translocation ◽  
Point Mutations ◽  
Amino Acid Residues ◽  
Transmembrane Helices ◽  
Inhibition Of Growth ◽  
Pneumococcal Strain ◽  
Resistant Strains ◽  
Related Compounds

ABSTRACT The activities of mefloquine (MFL) and related compounds against previously characterized Streptococcus pneumoniae strains carrying defined amino acid substitutions in the c subunit of the F0F1 H+-ATPase were studied. In addition, a series of MFL-resistant (Mflr) strains were isolated and characterized. A good correlation was observed between inhibition of growth and inhibition of the membrane-associated F0F1 H+-ATPase activity. MFL was about 10-fold more active than optochin and about 200-fold more active than quinine in inhibiting both the growth and the ATPase activities of laboratory pneumococcal strain R6. Mutant strains were inhibited by the different compounds to different degrees, depending on their specific mutations in the c subunit. The resistant strains studied had point mutations that changed amino acid residues in either the c subunit or the a subunit of the F0 complex. Changes in the c subunit were located in one of the two transmembrane α helices: residues M13, G14, G20, M23, and N24 of helix 1 and residues M44, G47, V48, A49, and V57 of helix 2. Changes in the a subunit were also found in either of the transmembrane α helices, helix 5 or 6: residue L186 of helix 5 and residues W206, F209, and S214 of helix 6. These results suggest that the transmembrane helices of the c and a subunits interact and that the mutated residues are important for the structure of the F0 complex and proton translocation.

scholarly journals The HIV-1 Vpu transmembrane domain topology and formation of a hydrophobic interface with BST-2 are critical for Vpu-mediated BST-2 downregulation

2020 ◽  
Author(s):  
Nabab Khan ◽  
Siladitya Padhi ◽  
Paresh Patel ◽  
U. Deva Priyakumar ◽  
Shahid Jameel
Keyword(s):  
Amino Acid ◽  
Transmembrane Domain ◽  
Virus Production ◽  
Cell Protein ◽  
Amino Acid Residues ◽  
Host Cell Protein ◽  
Immunodeficiency Virus ◽  
Molecular Modeling Studies ◽  
Hiv 1 ◽  
Hydrophobic Interface

AbstractViruses belonging to the M group of human immunodeficiency virus (HIV-1) are the most virulent among the four HIV-1 groups. One factor that distinguishes the M group HIV-1 from others is Vpu, a membrane localized accessory protein, which promotes the release of virions by neutralizing the antiviral host cell protein BST-2. To investigate if this activity is determined by the topology of Vpu or by conserved amino acid residues, we prepared chimeric forms of Vpu by replacing its transmembrane domain with those from its topological homologs. Although the chimeric Vpu proteins downregulated BST-2, these substantially reduced virus production as well. Molecular modeling studies on Vpu from different HIV-1 groups and the chimeric Vpu proteins showed that shape and the availability of a hydrophobic interface are more important for BST-2 antagonism than conservation of the amino acid sequence. Our data suggest that the HIV-1 Vpu-M protein has evolved topologically to interact with BST-2, and that the Vpu/BST-2 interface can be exploited as a target to limit HIV-1 replication.

Genetic Basis and Carrier Detection of Hemophilia B of Chinese Origin

1993 ◽  
Vol 69 (03) ◽  
pp. 247-252 ◽  
Author(s):  
Shu-Wha Lin ◽  
Ming-Ching Shen
Keyword(s):  
Amino Acid ◽  
Gene Deletion ◽  
Direct Sequencing ◽  
Screening Method ◽  
Point Mutations ◽  
Factor Ix ◽  
Hemophilia B ◽  
Sscp Analysis ◽  
Amino Acid Residues ◽  
Chinese Origin

SummaryWe have characterized the genetic defects of 17 hemophilia B patients of Chinese origin by means of the polymerase chain reaction (PCR) and direct sequencing. The single-strand conformation polymorphism (SSCP) was used as an initial screening method to analyze the entire coding region and the flanking introns of each individual’s factor IX gene. The abnormal exons were subsequently amplified and the nucleotide sequence determined. Of the 17 patients studied, 16 had single point mutations and one had a gross gene deletion of exons VII and VIII of factor IX. Among these 16 factor IX variants with point mutations 13 were missense and two were nonsense mutations. The remaining one had a nucleotide deleted, resulting in frame shifting at amino acid residue 97. A total of ten novel mutations, including the one with gross gene deletion, are reported in this study which have not been described previously. Five of the remaining seven variants were missense mutations with novel amino acids substituted for residues 127, 132, 180, 207, and 215, respectively. Mutations containing different amino acid residues at those positions have been reported. The last two are variants that have already been described to contain mutations at amino acid residues 333 and 365, respectively. To evaluate the efficiency of SSCP analysis in assessing the mutated exons and to further confirm our results we sequenced the entire exons of all 17 factor IX genes. The mutations detected by SSCP method were indeed the only mutation identified in each factor IX variant. The SSCP analysis and direct sequencing have also allowed us to circumvent the difficulties of carrier determination for Chinese by direct detection of the abnormal factor IX alleles inherited by the females.

scholarly journals Characterization of the Phd Repressor-Antitoxin Boundary

2005 ◽  
Vol 187 (2) ◽  
pp. 765-770 ◽  
Author(s):  
James Estle McKinley ◽  
Roy David Magnuson
Keyword(s):  
Amino Acid ◽  
Point Mutations ◽  
Modular Organization ◽  
Amino Acid Residues ◽  
The Third ◽  
Linear Sequence ◽  
C Terminus ◽  
Overlapping Sets ◽  
Repressor Activity

ABSTRACT The P1 plasmid addiction operon (a classic toxin-antitoxin system) encodes Phd, an unstable 73-amino-acid repressor-antitoxin protein, and Doc, a stable toxin. It was previously shown by deletion analysis that the N terminus of Phd was required for repressor activity and that the C terminus was required for antitoxin activity. Since only a quarter of the protein or less was required for both activities, it was hypothesized that Phd might have a modular organization. To further test the modular hypothesis, we constructed and characterized a set of 30 point mutations in the third and fourth quarters of Phd. Four mutations (PhdA36H, V37A, I38A, and F44A) had major defects in repressor activity. Five mutations (PhdD53A, D53R, E55A, F56A, and F60A) had major defects in antitoxin activity. As predicted by the modular hypothesis, point mutations affecting each activity belonged to disjoint, rather than overlapping, sets and were separated rather than interspersed within the linear sequence. A final deletion experiment demonstrated that the C-terminal 24 amino acid residues of Phd (preceded by a methionine) retained full antitoxin activity.

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