Receptors are protein molecules that receive chemical signals in the form of ligands and induce responses at cellular level. They are localized at the cell surface, cytoplasm or the nucleus, depending on their amino acid sequences. In addition to using these three different localizations to categorize receptors, the types of action of receptors are also used as a mean of classification. The four main classifications of receptors are: 1. Ionotropic (or ligand-gated ion channel) receptors, 2. G-protein coupled receptors (GPCR), 3. Enzyme or kinase linked receptors and 4. Nuclear receptors (not in terms of localization but effect on gene expression). Receptors are ligand-specific due to the unique structures of their binding sites which complement
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The IUPAC name of GABA is 4-amino butanoic acid (NH2CH2CH2 CH2COOH), though under physiological conditions GABA exists as an electroneutral zwitterion (NH3+CH2CH2 CH2COO-), with an isoelectric point of approximately 7.3, hence the appropriate name for GABA should be gamma aminobutyrate. There are two forms of GABA receptors: GABA(A) and GABA(B) receptor. The activation of these receptors primarily induce postsynaptic inhibition of neurons and this sedative or hypnotic feature of the receptors are highly significant in the CNS because they are the target of therapeutic drugs to treat psychiatric diseases such as anxiety disorder and so on. They are also responsible for the ‘light- headedness’ we feel when excessive alcohol is consumed as ethanol can mimic action of GABA and bind to GABA receptors and inhibit neuronal excitation. These receptors function in the exact opposite way compared to glutamate receptors which induce postsynaptic excitation of neurons. Out of the two, the receptor I will talk about is the GABAA …show more content…
The subunits are ‘chosen’ and assembled from a pool of 19 subunits (α1-6, β1-3, γ1-3, δ, ε, π, and ρ1-3), hence giving the possibility of a diverse isoform heterogeneity. In each subunit family, the members share about 70- 80% sequence homology whereas members from different subunit family share about 30- 40% sequence homology. The mature subunits are made up of approximately 450 amino acids residues and are identical in terms of topological organization. In each subunit, about half of it consists of extracellular N-terminal domain (made up of approximately 200 amino acids) which contains the Cys loop (loop formed by a disulfide bond between two cysteine residues which are separated by 13 amino acids), followed by four α-helical transmembrane domains (M1-4) each consisting of near 20 amino acids. Generally speaking, the M2 domain (made up of amino acids sequence: Thr-Thr-Val-Leu-Thr-Met-Thr (Ser) and a sum of eight Ser/Thr) forms the chloride ion channel. There is a large intracellular loop between M3 and M4, a site involved in phosphorylation regulation as well as interaction with some cytoplasmic proteins (not in all
The IUPAC name of GABA is 4-amino butanoic acid (NH2CH2CH2 CH2COOH), though under physiological conditions GABA exists as an electroneutral zwitterion (NH3+CH2CH2 CH2COO-), with an isoelectric point of approximately 7.3, hence the appropriate name for GABA should be gamma aminobutyrate. There are two forms of GABA receptors: GABA(A) and GABA(B) receptor. The activation of these receptors primarily induce postsynaptic inhibition of neurons and this sedative or hypnotic feature of the receptors are highly significant in the CNS because they are the target of therapeutic drugs to treat psychiatric diseases such as anxiety disorder and so on. They are also responsible for the ‘light- headedness’ we feel when excessive alcohol is consumed as ethanol can mimic action of GABA and bind to GABA receptors and inhibit neuronal excitation. These receptors function in the exact opposite way compared to glutamate receptors which induce postsynaptic excitation of neurons. Out of the two, the receptor I will talk about is the GABAA …show more content…
The subunits are ‘chosen’ and assembled from a pool of 19 subunits (α1-6, β1-3, γ1-3, δ, ε, π, and ρ1-3), hence giving the possibility of a diverse isoform heterogeneity. In each subunit family, the members share about 70- 80% sequence homology whereas members from different subunit family share about 30- 40% sequence homology. The mature subunits are made up of approximately 450 amino acids residues and are identical in terms of topological organization. In each subunit, about half of it consists of extracellular N-terminal domain (made up of approximately 200 amino acids) which contains the Cys loop (loop formed by a disulfide bond between two cysteine residues which are separated by 13 amino acids), followed by four α-helical transmembrane domains (M1-4) each consisting of near 20 amino acids. Generally speaking, the M2 domain (made up of amino acids sequence: Thr-Thr-Val-Leu-Thr-Met-Thr (Ser) and a sum of eight Ser/Thr) forms the chloride ion channel. There is a large intracellular loop between M3 and M4, a site involved in phosphorylation regulation as well as interaction with some cytoplasmic proteins (not in all