User:Snehalatha Kaliappan/Histamine

From Proteopedia

1 Structure of Histamine
2 References
3 Histamine H1 Receptor
4 References

Structure of Histamine

Histamine is an organic compound containing nitrogen atoms found in some of the human body cells. It is part of the immune system that causes the allergy related symptoms such as itching, sneezing and cold like symptoms. It also acts like a neurotransmitter in brain, spinal cord and uterus. It also regulates physiological functions in gut. The imidazole ring of the histamine can have two forms depending on which of the two nitrogens' is protonated. The nitrogens in the histamine are as follows: The nitrogen farther away from the side chain is the 'tele' nitrogen and is denoted by a lowercase tau sign and the nitrogen closer to the side chain is the 'pros' nitrogen and is denoted by the pi sign.The nitrogen on aminoethyl side chain is denoted by alpha. The tele tautomer, Nτ-H-histamine, is preferred in solution as compared to the pros tautomer, Nπ-H-histamine. Histamine has two basic nitrogen atoms. The alpha nitrogen and the pi nitrogen. Under physiological conditions the alpha nitrogen will be protonated. The pKa of the conjugated acid of alpha protonated histamine is 9.4 and pKa of Pi protonated histamine is 5.8.

References

https://en.wikipedia.org/wiki/Histamine https://www.sciencedirect.com/science/article/pii/S0166128003006523 https://www.researchgate.net/publication/235351330_Microsolvation_of_the_histamine_monocation_in_aqueous_solution_The_effect_on_structure_hydrogen_bonding_ability_and_vibrational_spectrum#pf2

Histamine H1 Receptor

Histamine receptors belong to class A of the GPCR superfamily(G protein‐coupled receptors) contain a bundle of seven antiparallel transmembrane helices. Histamine binds to these receptors as primary endogenous ligand. The crystal structure of the histamine H 1 receptor was obtained in 2011 and is still the only structure of histamine receptor deposited in the Protein Data Bank( PDB ID: 3RZE). It shows the crystal structure of the H1 receptor complex with doxepin, a first-generation H1 receptor antagonist. Doxepin sits deep in the and directly interacts with , a highly conserved key residue in G-protein-coupled-receptor activation.This well-conserved pocket with mostly hydrophobic nature contributes to the low selectivity of the first-generation compounds. The pocket is associated with an anion-binding region occupied by a phosphate ion. Docking of various second-generation H(1)R antagonists reveals that the unique carboxyl group present in this class of compounds with Lys 191 and/or Lys 179, both of which form part of the anion-binding region.