Record Details

Binding chemistry and molecular heterogeneity of neurotensin binding protein(s)/receptor in adult chicken tissues

NOPR - NISCAIR Online Periodicals Repository

View Archive Info
 
 
Field Value
 
Title Binding chemistry and molecular heterogeneity of neurotensin binding protein(s)/receptor in adult chicken tissues
 
Creator Mitra, Sankar P
 
Subject Neurotensin
Neurotensin receptor
Guanosine 5-O–[γ-thio] triphosphate
N-ethylmaleimide
125I-Neurotensin binding
Photoaffinity labeling
Photoactivatable azido analogues
G-protein coupled receptor
Antagonist SR48692
Levocabastine
Immune precipitation
 
Description 511-520
The study focuses on the importance of Tyr11
amino acid (AA) and subsequent stereochemistry involved in the binding process
of neurotensin (NT) with its receptor (NTR)/binding protein(s) as well as the size
heterogeneity. Using the binding of 125I-NT with several chicken
tissues, it is identified that one of the crucial factors behind all high
affinity (Kd ~10 pM)
interactions is due to phenolic-OH (Φ-OH) at the para (p) position of Tyr11 within
RRPYIL-CO2H (NT8-13) sequence. Replacing the p-OH only in Tyr11
by substituting with p-Cl, p-F and p-NH2 results in significant change of the binding
affinity (Kd); p-OH
≈ p-NH2 (~10 pM), p-Cl
(~100 pM), p-F (~120 pM). Interestingly, p-NH2 equals to p-OH
displaying the highest affinity. Experiments conducted by binding several of
the 125I-azido–NT analogs having azido group attached at different
positions within the NT molecule have further confirmed the necessity of RRPYIL
sequence for high affinity ligand-receptor interaction. The role of Tryp11
in place of Tyr11 in addition to the results above establishes a
significant possibility of H–bonding occurring between p-OH of NT and NTR inside the docking space. Photo labeling of the
liver tissue by substituted 125I-Y3-azido-NT analogs
shows several specifically labeled bands with considerable range of molecular
weight (Mr ~90-30 kDa) variations. These
results indicate the existence of molecular heterogeneity concerning the sizes
of NTR or else any NT binding proteins in the avian tissues. Further,
the study has revealed that besides liver, several other chicken tissues also
express similar specific high affinity binding (Kd ~20 pM) with varying capacities (Bmax).
The order for Bmax is: liver (1.2 pMol/mg)  gall bladder (1.03 pMol/mg) > spleen (0.43
pMol/mg) > brain (0.3 pMol/mg)
> colon lung (0.15 pMol/mg). In all
cases, the binding was reduced by GTPgS (ED50 ~ 0.05 nM), NEM
(ED50 ~ 0.50 mM)
and NaCl (ED50 ~30 mM), indicating the existence of NTR identical to
the mammalian type-1.
 
Date 2013-12-27T11:31:05Z
2013-12-27T11:31:05Z
2013-12
 
Type Article
 
Identifier 0975-0959 (Online); 0301-1208 (Print)
http://hdl.handle.net/123456789/25165
 
Language en_US
 
Rights CC Attribution-Noncommercial-No Derivative Works 2.5 India
 
Publisher NISCAIR-CSIR, India
 
Source IJBB Vol.50(6) [December 2013]