Amino acid sequence receptor

There are many different STAT proteins, each with a slightly different amino acid sequence. Receptors for different cytokines bind different STATs, which then form heterodimers in various combinations. This microheterogeneity allows different cytokines to target different genes. 

Fig. 5. Schematic diagram of the presumed arrangement of the amino acid sequence for the 5-opioid receptor, showing seven putative transmembrane segments three intracellular loops, A three extracellular loops, B the extracellular N-terrninus and the intracellular C-terrninus, where (0) represents amino acid residues common to ] -, 5-, and K-receptors ( ), amino acid residues common to all three opioid receptors and other neuropeptide receptors and (O), other amino acids. Branches on the N-terruinal region indicate possible glycosylation sites, whereas P symbols in the C-terminal region indicate...

FIGURE 1.4 Increasing levels of protein structure. A protein has a given amino acid sequence to make peptide chains. These adopt a 3D structure according to the free energy of the system. Receptor function can change with changes in tertiary or quaternary structure. 

Apelins and the Apelin Receptor. Figure 2 Sequence alignment of mammalian and amphibian apelin-36 amino-acid sequences, indicates residues conserved across all the species shown. Residues which differfrom the human sequence are highlighted in red. 

Several splice variants of MOP (formerly MOR-1) have been cloned (MOP-1A to MOR-1X). The B, C, andD variants differ in their amino acid sequence at the C-terminal end [4]. These receptor valiants differ in their distribution in the central nervous system and in the rate of internalization and desensitization upon... 

Prostanoids. Figure 2 EP3 receptor sequence of three mouse EP3 receptor splice variants differing only in their intracellular carboxyl termini. The predicted amino acid sequences of each splice variant are represented by the one letter amino acid code. The common region is comprised of two exons, which are spliced to three possible C-terminal tails. The carboxyl variable tails are designated alpha, beta, and gamma,each encoded by distinct exons. 

The common C-terminal amino acid sequence required for exerting activity at tachykinin receptors is shown in bold endokinin C and D lack the C-terminal Met and are almost devoid of affinity at these receptors. In red, the sequence of neurokinin A of which neuropeptide-gamma and neuropeptide-kappa are elongated forms and neurokinin A (3-10) is a product of beta or gamma-TAC1 mRNAs or an NKA metabolite active at tachykinin receptors. In blue, the sequence of human HK-1 of which endokinin A and B are elongated forms. 

The structure of all TK receptors is similar in terms of expression oiTACR genes, since all these genes contain five exons intercalated by four introns [1, 5]. Exon I encodes for the N-terminal extracellular tail, the first intracellular (IC1) and extracellular (EC1) loops and the first, second, and third transmembrane domains (TM1, TM2, and TM3). Exon II encodes for the second intracellular (IC2) and extracellular (EC2) loops and the fourth transmembrane domain (TM4). Exon III encodes for the fifth transmembrane domain (TM5) and the third intracellular loop (IC3). Exon IV encodes for the sixth and seventh transmembrane domains (TM6 and TM7) and the third extracellular loop. Exon V encodes for the C-terminal intracellular tail only. A schematic drawing of the amino acid sequences and TK receptor organization is shown in Fig. 1. 

A comparison of several different steroid receptors with thyroid hormone receptors revealed a remarkable conservation of the amino acid sequence in certain regions, particularly in the DNA-binding domains. This led to the realization that receptors of the steroid or thyroid type are members of a large superfamily of nuclear receptors. Many related members of this family have no known ligand at present and thus are called orphan receptors. The nuclear receptor superfamily plays a critical role in the regulation of gene transcription by hormones, as described in Chapter 43. 

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