Structural Basis of Functional Mimicry between Carbohydrate and Peptide Ligands of Con A

2000 ◽  
Vol 272 (3) ◽  
pp. 843-849 ◽  
Author(s):  
Deepti Jain ◽  
Kanwal J. Kaur ◽  
Manisha Goel ◽  
Dinakar M. Salunke
Keyword(s):  
Peptide Ligands ◽  
Structural Basis ◽  
Con A

Structural Determinants for Signal Transducer and Activator of Transcription (STAT) 3 Recruitment and Activation by the Granulocyte Colony-Stimulating Factor Receptor (G-CSFR) at Phosphotyrosine Ligands 704 and 744.

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 2169-2169
Author(s):  
David John Tweardy ◽  
Xu Xuejun ◽  
Naijie Jing ◽  
Huang Shao
Keyword(s):  
Ligand Binding ◽  
Sh2 Domain ◽  
Peptide Ligands ◽  
Full Length ◽  
Myelogenous Leukemia ◽  
Structural Basis ◽  
Side Chain ◽  
Amide Hydrogen ◽  
Wild Type ◽  
Structural Determinants

Abstract Four tyrosine (Y) residues within the cytoplasmic domain of the G-CSFR (Y704, Y228, Y744 and Y764 in the human receptor; Y703, Y227, Y743 and Y763 in the murine receptor) become phosphorylated by Jak kinases upon ligand binding leading to recruitment of Src homology (SH) 2 domain-containing proteins that link to programs for myeloid cell survival and differentiation (Stat3 recruitment to Y704 and Y744) and proliferation (SHP-2 and PI3K recruitment to Y04; Grb2, Shc and SHP-2 recruitment to Y764). While the preference of SH2 domain binding to specific phospho (p) Y peptide ligands was shown to map to the three residues immediately C-terminal to the pY (+1, +2, +3 residues), the structural basis for these preferences is poorly understood but could be exploited to specifically target deleterious G-CSFR-mediated signaling events such as aberrant Stat3 activation, which has been demonstrated in a subset of acute myelogenous leukemia (AML) patients whose cells contain Flt3 internal tandem duplications and who suffer relapse following initial chemotherapy. To establish the structural basis for Stat3 recruitment and activation by the G-CSFR at Y704 and Y744, we generated purified recombinant full-length Stat3 and phosphododecapeptides based on the sequence surrounding each Y within the G-CSFR. In peptide pull-down assays, recombinant Stat3 bound only to Y704 and Y744 phosphododecapeptide, which contain core pY motifs consisting of pYVLQ and pYLRC, respectively. In mirror resonance affinity assays employed to obtain quantitative binding information, Stat3 bound to each phosphododecapeptide with similar kinetics (e.g. KDs = 0.703 and 0.95 μM, respectively). We tested three models for Stat3 SH2-pY ligand binding proposed by us and others using wild type and mutant recombinant Stat3 proteins in peptide pull-down and mirror resonance affinity assays along with computer modeling of this interaction using the known structures of Statβ SH2 and EGFR pY ligand (EpY1068INQ). Our results revealed loss of binding of Stat3 to Y704 and Y744 phosphododecapeptides only in Stat3 mutated within the SH2 domain at K591 or R609, whose side chains interacted with the pY phosphate group, and in Stat3 mutated within the SH2 domain at E638, whose amide hydrogen bonded with oxygen within the +3 Q side chain (or with sulfur within the +3 C side chain) when the pY ligand assumes a β turn. G-CSF stimulation of cells co-expressing full-length G-CSFR and either wild type or mutant Stat3 constructs confirmed the requirements for the side chain of R609 and the amide hydrogen of E638 within the Stat3 SH2 domain for binding to the G-CSFR and subsequent phosphorylation of Stat3 on Y705. Thus, our findings identify for the first time the structural basis for recruitment and activation of Stat3 by the G-CSFR and reveal unique features of their interaction at Y704 and Y744 i.e. a β turn within the receptor pY motif and a key hydrogen bond formed between the polar side chain of the +3 residue and the amide hydrogen of E638 within the Stat3 SH2 domain. These features explain the preference of the Stat3 SH2 domain for pY peptide ligands with +3 Q or C as well as +3 T (pY705LKT within Stat3) and +3 S (pY743IRS within the murine G-CSFR) and can be exploited using a structure-assisted drug design strategy to develop new therapies for a subset of AML patients with poor prognosis whose cells demonstrate aberrant activation of Stat3.

scholarly journals Structural basis for T cell recognition of altered peptide ligands: a single T cell receptor can productively recognize a large continuum of related ligands.

1996 ◽  
Vol 184 (4) ◽  
pp. 1259-1268 ◽  
Author(s):  
G J Kersh ◽  
P M Allen
Keyword(s):  
T Cell ◽  
T Cell Receptor ◽  
Cell Clone ◽  
Cell Receptor ◽  
Peptide Ligands ◽  
Structural Basis ◽  
Side Chain ◽  
Contact Residue ◽  
Altered Peptide Ligands ◽  
T Cell Clone

T cells recognize short linear peptides bound to major histocompatibility complex (MHC)-encoded molecules. Subtle molecular changes in peptide antigens produce altered peptide ligands (APLs), which induce different T cell responses from those induced by the antigenic ligand. A molecular basis for how these slight molecular variations lead to such different consequences for the T cell has not been described. To address this issue, we have made amino acid substitutions at the primary T cell receptor (TCR) contact residue of the murine hemoglobin determinant, Hb(64-76)/I-Ek and produced 12 peptides that interact with the TCR of the T cell clone 3.L2. The 3.L2 T cell responds to these peptides, which vary 1 million-fold in their activity, and enables them to be ranked according to their relative ability to signal through the 3.L2 TCR. Such a ranking reveals that the ability of the 3.L2 T cell to respond to these peptides depends on how well the structure of the side chain at the primary TCR contact site mimics that of the Asn residue present in the antigenic ligand. The reactivity of the 3.L2 T cell also depends on an MHC contact residue that is next to the primary TCR contact residue, suggesting that conformation of the Asn side chain is also important. By using nonnatural amino acids at a TCR contact residue, we have demonstrated that APLs can be rationally designed based on structure. These data are consistent with a model in which the affinity of a peptide-MHC complex for the TCR determines how the T cell will respond.

A structural basis for four distinct elution profiles on concanavalin A – Sepharose affinity chromatography of glycopeptides

1979 ◽  
Vol 57 (1) ◽  
pp. 83-96 ◽  
Author(s):  
Saroja Narasimhan ◽  
James R. Wilson ◽  
Eva Martin ◽  
Harry Schachter
Keyword(s):  
Affinity Chromatography ◽  
Weak Interaction ◽  
Concanavalin A ◽  
Tight Binding ◽  
Structural Basis ◽  
Con A ◽  
Mannose Residue ◽  
Terminal Residue ◽  
The Third ◽  
Profile Type

Twelve 14C-acetylated glycopeptides have been subjected to affinity chromatography on concanavalin A (Con A) – Sepharose at pH 7.5. The elution profiles could be classified into four distinct patterns. The first pattern showed no retardation of glycopeptide on the column and was elicited with a glycopeptide having three peripheral oligosaccharide chains:[Formula: see text]Such glycopeptides have only a single mannose residue capable of interacting with Con A – Sepharose; an interacting mannose residue is either an α-linked nonreducing terminal residue or an α-linked 2-O-substituted residue. The second type of profile showed a retarded elution of glycopeptide with buffer lacking methyl α-D-glucopyranoside (indicative of weak interaction with the column) and was given by glycopeptides with the structures:[Formula: see text]where R1 is either H or a sialyl residue. The third profile type showed tight binding of glycopeptide to Con A – Sepharose and elution as a sharp peak with 0.1 M methyl α-D-glucopyranoside; glycopeptides giving this pattern had the structures:[Formula: see text]where R2 is either H, GlcNAc, Gal-β1,4-GlcNAc, or sialyl-Gal-β1,4-GlcNAc. These glycopeptides all have two interacting mannose residues, the minimum required for binding to the column; one of these mannose residues must, however, be a terminal residue to obtain tight binding and sharp elution. The fourth profile type showed tight binding of glycopeptide to the column but elution with 0.1 M methyl α-D-glucopyranoside resulted in a broad peak indicating very tight binding; glycopeptides showing this behaviour had the structures:[Formula: see text]where R3 is either GlcNAc, Gal-β1,4-GlcNAc, or siaryl-Gal-β1,4-GlcNAc. Therefore it can be concluded that although a minimum of two interacting mannose residues is required for binding to Con A – Sepharose, the residues linked to these mannoses can either strengthen or weaken binding to the column.

scholarly journals A Structural Basis for CD8+T Cell-dependent Recognition of Non-homologous Peptide Ligands

2005 ◽  
Vol 280 (29) ◽  
pp. 27069-27075 ◽  
Author(s):  
Tatyana Sandalova ◽  
Jakob Michaëlsson ◽  
Robert A. Harris ◽  
Jacob Odeberg ◽  
Gunter Schneider ◽  
...  
Keyword(s):  
T Cell ◽  
Cd8 T Cell ◽  
Peptide Ligands ◽  
Structural Basis ◽  
Homologous Peptide

Organization of tight junctions in the choroid plexus epithelium

1978 ◽  
Vol 36 (2) ◽  
pp. 336-337
Author(s):  
B. Van Deurs ◽  
J. K. Koehler
Keyword(s):  
Choroid Plexus ◽  
Present Report ◽  
Freeze Fracture ◽  
Barrier Properties ◽  
Cell Junctions ◽  
Structural Basis ◽  
Apical Surface ◽  
Choroid Plexus Epithelium ◽  
Solid Nitrogen ◽  
Special Composition

The choroid plexus epithelium constitutes a blood-cerebrospinal fluid (CSF) barrier, and is involved in regulation of the special composition of the CSF. The epithelium is provided with an ouabain-sensitive Na/K-pump located at the apical surface, actively pumping ions into the CSF. The choroid plexus epithelium has been described as “leaky” with a low transepithelial resistance, and a passive transepithelial flux following a paracellular route (intercellular spaces and cell junctions) also takes place. The present report describes the structural basis for these “barrier” properties of the choroid plexus epithelium as revealed by freeze fracture.Choroid plexus from the lateral, third and fourth ventricles of rats were used. The tissue was fixed in glutaraldehyde and stored in 30% glycerol. Freezing was performed either in liquid nitrogen-cooled Freon 22, or directly in a mixture of liquid and solid nitrogen prepared in a special vacuum chamber. The latter method was always used, and considered necessary, when preparations of complementary (double) replicas were made.

Lectin Binding Studies on RNA Tumor Virus-Infected Cells

1975 ◽  
Vol 33 ◽  
pp. 326-327
Author(s):  
D. C. Hixson
Keyword(s):  
Binding Sites ◽  
Lectin Binding ◽  
Culture Conditions ◽  
3T3 Cells ◽  
Binding Studies ◽  
Con A ◽  
Microscopic Studies ◽  
Tumor Virus ◽  
Infected Cells ◽  
Cell Culture Conditions

The abilities of plant lectins to preferentially agglutinate malignant cells and to bind to specific monosaccharide or oligosaccharide sequences of glycoproteins and glycolipids make them a new and important biochemical probe for investigating alterations in plasma membrane structure which may result from malignant transformation. Electron and light microscopic studies have demonstrated clustered binding sites on surfaces of SV40-infected or tryp- sinized 3T3 cells when labeled with concanavalin A (con A). No clustering of con A binding sites was observed in normal 3T3 cells. It has been proposed that topological rearrangement of lectin binding sites into clusters enables con A to agglutinate SV40-infected or trypsinized 3T3 cells (1). However, observations by other investigators have not been consistent with this proposal (2) perhaps due to differences in reagents used, cell culture conditions, or labeling techniques. The present work was undertaken to study the lectin binding properties of normal and RNA tumor virus-infected cells and their associated viruses using lectins and ferritin-conjugated lectins of five different specificities.

High resolution spot scan imaging of frozen, hydrated actin bundles with 400kV electrons

1992 ◽  
Vol 50 (1) ◽  
pp. 512-513
Author(s):  
J. Jakana ◽  
M.F. Schmid ◽  
P. Matsudaira ◽  
W. Chiu
Keyword(s):  
High Resolution ◽  
Binding Proteins ◽  
Actin Binding ◽  
Eukaryotic Cells ◽  
Dimensional Structure ◽  
Structural Basis ◽  
Actin Bundle ◽  
Actin Bundles ◽  
3 Dimensional ◽  
Macromolecular Assembly

Actin is a protein found in all eukaryotic cells. In its polymerized form, the cells use it for motility, cytokinesis and for cytoskeletal support. An example of this latter class is the actin bundle in the acrosomal process from the Limulus sperm. The different functions actin performs seem to arise from its interaction with the actin binding proteins. A 3-dimensional structure of this macromolecular assembly is essential to provide a structural basis for understanding this interaction in relationship to its development and functions.

Electron Microscopy and image reconstruction reveal the structural basis for spectrin's elastic properties

1992 ◽  
Vol 50 (1) ◽  
pp. 510-511
Author(s):  
Amy M. McGough ◽  
Robert Josephs
Keyword(s):  
Electron Microscopy ◽  
Elastic Properties ◽  
Conformational Changes ◽  
Quaternary Structure ◽  
Three Dimensional ◽  
Membrane Skeleton ◽  
Projection Algorithm ◽  
Structural Basis ◽  
Iterative Approximation ◽  
Membrane Skeletons

The remarkable deformability of the erythrocyte derives in large part from the elastic properties of spectrin, the major component of the membrane skeleton. It is generally accepted that spectrin's elasticity arises from marked conformational changes which include variations in its overall length (1). In this work the structure of spectrin in partially expanded membrane skeletons was studied by electron microscopy to determine the molecular basis for spectrin's elastic properties. Spectrin molecules were analysed with respect to three features: length, conformation, and quaternary structure. The results of these studies lead to a model of how spectrin mediates the elastic deformation of the erythrocyte.Membrane skeletons were isolated from erythrocyte membrane ghosts, negatively stained, and examined by transmission electron microscopy (2). Particle lengths and end-to-end distances were measured from enlarged prints using the computer program MACMEASURE. Spectrin conformation (straightness) was assessed by calculating the particles’ correlation length by iterative approximation (3). Digitised spectrin images were correlation averaged or Fourier filtered to improve their signal-to-noise ratios. Three-dimensional reconstructions were performed using a suite of programs which were based on the filtered back-projection algorithm and executed on a cluster of Microvax 3200 workstations (4).

Electron diffraction detection of ordliking in annealed PbTe thin film

1990 ◽  
Vol 48 (4) ◽  
pp. 1018-1019
Author(s):  
Karimat El-Sayed
Keyword(s):  
Thin Film ◽  
Electron Diffraction ◽  
Lead Telluride ◽  
Structural Basis ◽  
Face Centered Cubic ◽  
X Ray ◽  
Polycrystalline Thin Films ◽  
Stage Process ◽  
Diffraction Patterns ◽  
Face Centered

Lead telluride is an important semiconductor of many applications. Many Investigators showed that there are anamolous descripancies in most of the electrophysical properties of PbTe polycrystalline thin films on annealing. X-Ray and electron diffraction studies are being undertaken in the present work in order to explain the cause of this anamolous behaviour.Figures 1-3 show the electron diffraction of the unheated, heated in air at 100°C and heated in air at 250°C respectively of a 300°A polycrystalline PbTe thin film. It can be seen that Fig. 1 is a typical [100] projection of a face centered cubic with unmixed (hkl) indices. Fig. 2 shows the appearance of faint superlattice reflections having mixed (hkl) indices. Fig. 3 shows the disappearance of thf superlattice reflections and the appearance of polycrystalline PbO phase superimposed on the [l00] PbTe diffraction patterns. The mechanism of this three stage process can be explained on structural basis as follows :

Sign in / Sign up

Export Citation Format

Share Document