Amino Acids, Proteins and Porphyrins
In terms of chemical structure, which one of the following is a tetrameric glycoprotein?
Insulin Receptor: Mol. Wt-340,000, is a Tetrameres, made up 2 α and 2βglycoprotein subunits. The gene for Insulin Receptor-has 22 exons and is located on chromosome 19. The α - subunits binds with Insulin and are extra-cellular, while β-subunits span across the cell membrane, and their intracellular parts have Tyrosine kinase activity.
a. Leptin: contain 167 amino acids, acts on leptin receptors present in choroid plexuses and hypothalamus (Arcuate nuclei). Leptin receptor is a single membrane-spanning protein that resemble the signal — transducing component of IL-6. When Leptin Receptors are stimulated by leptin decrease food intake and increase Energy output -
b. Neuropeptide Y : increase food intake, is only part of the efferent appetite regulating pathway
c. Thyrotropin, TSH : i.e. thyroid — stimulating — hormone -
A. Secreted from anterior pituitary
B. TSH→is a glycoprotein, contain 211 amino acids, plus hexoses, hexosamines and sialic acid,
made up α of βand subunits.
C. The TSH receptor (Glycoprotein) is a typical serpentine receptor that activate adenylcyclase
throughGs. Serpentine receptor means that these span the membrane seven times. (T-trans membrane)