The Role of Ligand Binding in the Kinetic Folding Mechanism of Human p21H-rasProtein†

Biochemistry ◽  
1998 ◽  
Vol 37 (42) ◽  
pp. 14891-14899 ◽  
Author(s):  
Jing Zhang ◽  
C. Robert Matthews
Keyword(s):  
Ligand Binding ◽  
Folding Mechanism ◽  
Kinetic Folding

scholarly journals The role of Val68(E11) in ligand binding to sperm whale myoglobin. Site-directed mutagenesis of a synthetic gene.

1990 ◽  
Vol 265 (20) ◽  
pp. 11788-11795
Author(s):  
K D Egeberg ◽  
B A Springer ◽  
S G Sligar ◽  
T E Carver ◽  
R J Rohlfs ◽  
...  
Keyword(s):  
Ligand Binding ◽  
Sperm Whale ◽  
Site Directed Mutagenesis ◽  
Synthetic Gene ◽  
Directed Mutagenesis ◽  
Sperm Whale Myoglobin

scholarly journals The role of diffusion in limiting the rate of ligand binding to hemoglobin.

1980 ◽  
Vol 255 (17) ◽  
pp. 8050-8053
Author(s):  
R.J. Morris ◽  
Q.H. Gibson
Keyword(s):  
Ligand Binding

Role of Ionic Interactions in Ligand Binding and Catalysis of R67 Dihydrofolate Reductase†

Biochemistry ◽  
2003 ◽  
Vol 42 (36) ◽  
pp. 10569-10578 ◽  
Author(s):  
Stephanie N. Hicks ◽  
R. Derike Smiley ◽  
J. Bradley Hamilton ◽  
Elizabeth E. Howell
Keyword(s):  
Ligand Binding ◽  
Dihydrofolate Reductase ◽  
Ionic Interactions ◽  
R67 Dihydrofolate Reductase

scholarly journals Cooperative Interaction of Nck and Lck Orchestrates Optimal TCR Signaling

Cells ◽  
2021 ◽  
Vol 10 (4) ◽  
pp. 834
Author(s):  
Frederike A. Hartl ◽  
Jatuporn Ngoenkam ◽  
Esmeralda Beck-Garcia ◽  
Liz Cerqueira ◽  
Piyamaporn Wipa ◽  
...  
Keyword(s):  
T Cell ◽  
Ligand Binding ◽  
T Cell Activation ◽  
Cell Activation ◽  
Adaptor Protein ◽  
Cooperative Interaction ◽  
Tcr Signaling ◽  
Binding Motifs ◽  
Adaptive Immune

The T cell antigen receptor (TCR) is expressed on T cells, which orchestrate adaptive immune responses. It is composed of the ligand-binding clonotypic TCRαβ heterodimer and the non-covalently bound invariant signal-transducing CD3 complex. Among the CD3 subunits, the CD3ε cytoplasmic tail contains binding motifs for the Src family kinase, Lck, and the adaptor protein, Nck. Lck binds to a receptor kinase (RK) motif and Nck binds to a proline-rich sequence (PRS). Both motifs only become accessible upon ligand binding to the TCR and facilitate the recruitment of Lck and Nck independently of phosphorylation of the TCR. Mutations in each of these motifs cause defects in TCR signaling and T cell activation. Here, we investigated the role of Nck in proximal TCR signaling by silencing both Nck isoforms, Nck1 and Nck2. In the absence of Nck, TCR phosphorylation, ZAP70 recruitment, and ZAP70 phosphorylation was impaired. Mechanistically, this is explained by loss of Lck recruitment to the stimulated TCR in cells lacking Nck. Hence, our data uncover a previously unknown cooperative interaction between Lck and Nck to promote optimal TCR signaling.

Ligand modulates the conversion of DNA-bound vitamin D3 receptor (VDR) homodimers into VDR-retinoid X receptor heterodimers

1994 ◽  
Vol 14 (5) ◽  
pp. 3329-3338
Author(s):  
B Cheskis ◽  
L P Freedman
Keyword(s):  
Ligand Binding ◽  
Vitamin D3 ◽  
Hormone Receptors ◽  
Steroid Receptors ◽  
Dependent Manner ◽  
D3 Receptor ◽  
Vitamin D3 Receptor ◽  
Binding Domains

Protein dimerization facilitates cooperative, high-affinity interactions with DNA. Nuclear hormone receptors, for example, bind either as homodimers or as heterodimers with retinoid X receptors (RXR) to half-site repeats that are stabilized by protein-protein interactions mediated by residues within both the DNA- and ligand-binding domains. In vivo, ligand binding among the subfamily of steroid receptors unmasks the nuclear localization and DNA-binding domains from a complex with auxiliary factors such as the heat shock proteins. However, the role of ligand is less clear among nuclear receptors, since they are constitutively localized to the nucleus and are presumably associated with DNA in the absence of ligand. In this study, we have begun to explore the role of the ligand in vitamin D3 receptor (VDR) function by examining its effect on receptor homodimer and heterodimer formation. Our results demonstrate that VDR is a monomer in solution; VDR binding to a specific DNA element leads to the formation of a homodimeric complex through a monomeric intermediate. We find that 1,25-dihydroxyvitamin D3, the ligand for VDR, decreases the amount of the DNA-bound VDR homodimer complex. It does so by significantly decreasing the rate of conversion of DNA-bound monomer to homodimer and at the same time enhancing the dissociation of the dimeric complex. This effectively stabilizes the bound monomeric species, which in turn serves to favor the formation of a VDR-RXR heterodimer. The ligand for RXR, 9-cis retinoic acid, has the opposite effect of destabilizing the heterodimeric-DNA complex. These results may explain how a nuclear receptor can bind DNA constitutively but still act to regulate transcription in a fully hormone-dependent manner.

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