Calcium-sensing receptor in GtoPdb v.2021.3

The calcium-sensing receptor (CaS, provisional nomenclature as recommended by NC-IUPHAR [47] and subsequently updated [77]) responds to multiple endogenous ligands, including extracellular calcium and other divalent/trivalent cations, polyamines and polycationic peptides, L-amino acids (particularly L-Trp and L-Phe), glutathione and various peptide analogues, ionic strength and extracellular pH (reviewed in [78]). While divalent/trivalent cations, polyamines and polycations are CaS receptor agonists [14, 110], L-amino acids, glutamyl peptides, ionic strength and pH are allosteric modulators of agonist function [36, 47, 61, 108, 109]. Indeed, L-amino acids have been identified as "co-agonists", with both concomitant calcium and L-amino acid binding required for full receptor activation [148, 54]. The sensitivity of the CaS receptor to primary agonists is increased by elevated extracellular pH [18] or decreased extracellular ionic strength [109]. This receptor bears no sequence or structural relation to the plant calcium receptor, also called CaS.

An Intracellular Human Single Chain Antibody to Matrix Protein (M1) of H5N1 Virus

Background: Influenza virus matrix protein M1 is encoded by viral RNA fragment 7 and is the most abundant protein in virus particles. M1 is expressed in the late stages of viral replication and exerts functionality by inhibiting viral transcription. The M1 protein sequence is an attractive target for antibody drugs.Methods: The M1 protein sequence was amplified by RT-PCR using cDNA from the H5N1 virus as a template; the M1 protein was then expressed and purified. A human strain, high affinity, and single chain antibody (HuScFv) against M1 protein was obtained by phage antibody library screening using M1 as an antigen. A recombinant TAT-HuScFv protein was expressed by fusion with the TAT protein transduction domain (PTD) gene of HIV to prepare a human intracellular antibody against avian influenza virus. The differences between HuScFv and TAT-HUScFv were verified by various experiments and the amino acid binding site of the M1 protein was determined.Results: The M1 protein of H5N1, HuScFv, and TAT-HuScFv, were successfully purified and expressed by and in E. coli. Further analysis demonstrated that TAT-HuScFv inhibited the hemagglutination activity of the 300TCID50 H1N1 virus, thus providing preliminary validation of the universality of the antibody. After two rounds of M1 protein decomposition, the TAT-HuScFv antigen binding site was identified as Alanine (A) at position 239. Collectively, our data describe a recombinant antibody with high binding activity against the conserved sequences of avian influenza viruses. This intracellular recombinant antibody blocked the M1 protein that infected intracellular viruses, thus inhibiting the replication and reproduction of H5N1 viruses.Conclusion: Recombinant HuScFv was successfully identified using the Tomlinson (I+J) phage antibody library and successfully linked to the TAT protein transductive domain of the HIV virus. Compared with the HuScFv, the addition of the TAT peptide improved its ability to penetrate the cell membrane. A definite amino acid binding site was identified after the decomposition of M1 protein, thus providing a target and reference for the development of antibody drugs and the study of new drugs.

Calcium-sensing receptor (version 2020.5) in the IUPHAR/BPS Guide to Pharmacology Database

The calcium-sensing receptor (CaS, provisional nomenclature as recommended by NC-IUPHAR [46] and subsequently updated [76]) responds to multiple endogenous ligands, including extracellular calcium and other divalent/trivalent cations, polyamines and polycationic peptides, L-amino acids (particularly L-Trp and L-Phe), glutathione and various peptide analogues, ionic strength and extracellular pH (reviewed in [77]). While divalent/trivalent cations, polyamines and polycations are CaS receptor agonists [14, 109], L-amino acids, glutamyl peptides, ionic strength and pH are allosteric modulators of agonist function [35, 46, 60, 107, 108]. Indeed, L-amino acids have been identified as "co-agonists", with both concomitant calcium and L-amino acid binding required for full receptor activation [147, 53]. The sensitivity of the CaS receptor to primary agonists is increased by elevated extracellular pH [17] or decreased extracellular ionic strength [108]. This receptor bears no sequence or structural relation to the plant calcium receptor, also called CaS.

SWOTein: A structure-based approach to predict stability Strengths and Weaknesses of prOTEINs

MotivationAlthough structured proteins adopt their lowest free energy conformation in physiological conditions, the individual residues are generally not in their lowest free energy conformation. Residues that are stability weaknesses are often involved in functional regions, whereas stability strengths ensure local structural stability. The detection of strengths and weaknesses provides key information to guide protein engineering experiments aiming to modulate folding and various functional processes.ResultsWe developed the SWOTein predictor which identifies strong and weak residues in proteins on the basis of three types of statistical energy functions describing local interactions along the chain, hydrophobic forces and tertiary interactions. The large-scale comparison of the different types of strengths and weaknesses showed their complementarity and the enhancement of the information they provide. We applied SWOTein to apocytochrome b562 and found good agreement between predicted strengths and weaknesses and native hydrogen exchange data. Its application to an amino acid-binding protein identified the hinge at the basis of the conformational change. SWOTein is both fast and accurate and can be applied at small and large scale to analyze and modulate folding and molecular recognition processes.AvailabilityThe SWOTein webserver provides the list of predicted strengths and weaknesses and a protein structure visualization tool that facilitates the interpretation of the predictions. It is freely available for academic use at http://babylone.ulb.ac.be/SWOTein.