Q1) The steroid hormone receptors A. are membrane bound receptors for steroid ho
ID: 172062 • Letter: Q
Question
Q1) The steroid hormone receptors A. are membrane bound receptors for steroid hormones that signal ligand binding through a complex G-protein pathway. B. simultaneously bind hormones, DNA, and proteins. C. contain zinc finger DNA binding domains with Zn atoms coordinated by 2 cysteines and 2 histidine residues. D. all recognize the same DNA response element.
Q2) Thyroid hormone receptors A. are histone proteins localized in the chromatin of target cells. B. are intrinsic non-histone chromosomal proteins. C. initially bind triiodothyronine in the cytoplasm and after undergoing a conformational change translocate to the nucleus. D. are enzymes that deiodinate thyroxine to triiodothyronine. E. have higher affinity for thyroxine than triiodothyronine.
Explanation / Answer
Answer 1: (B) simultaneously bind hormones, DNA, and proteins
Steroid receptors of the nuclear receptor family and depending upon the type of receptor, they are either located in the cytosol (type I) and move to the cell nucleus upon activation, or remain in the nucleus (type II) waiting for the steroid hormone to enter and activate them. Only type I receptors have a heat shock protein (HSP) associated with the inactive receptor that will be released when the receptor interacts with the ligand. Type II nuclear receptors have no HSP, and in contrast to the classical type I receptor are located in the cell nucleus. Type II receptors are located in the nucleus. Thus, their ligands pass through the cell membrane and cytoplasm and enter the nucleus where they activate the receptor without release of HSP. The activated receptor interacts with the hormone response element and further transcription process is initiated. Therefore steroid hormone receptors (type II) can bind simultaneously with hormones, DNA, and proteins. There are following other properties of steroid hormone receptors
Answer 1: (B) Intrinsic non-histone chromosomal proteins
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