Response element AGAACA nnn TGTTCt Glucocorticoid TCTTGT nnn ACAAGA receptor AGGTCA nnn TGACCT Estrogen TCCAGT nnn ACTGGA receptor AGGTCa nnnnn AGACCA Retinoic TCCAGT nnnnn TCTGGT acid receptor AGGTCA TGACCT Thyroxine TCCAGT/ ACTGGA receptor AGGTca nnn AGGTCa Vitamin D TCCAGT nnn TCCAGT receptor
Some imported signaling compounds influence genome activity indirectly Glucose level is high CAMP level is low 0-P-0-P-0-P-0-CH2Adenine lacz No transcription ATP H OH OH Adenylate cyclase inhibited by glucose CAP detached via lIA GIc Adenine Glucose level is low cAMP level is high CAMP lacZ O=P-O OH CAMP CAP attaches to the cap site Transcription
Some imported signaling compounds influence genome activity indirectly
14.1.2. Signal transmission mediated by cell surface receptors Many extracellular signaling compounds are unable to enter the cell because they are too hydrophilic to penetrate the lipid membrane and the cell lacks a specific transport mechanism for their uptake Binding of the signaling compound results in a conformational change in the receptor, inducing a biochemical event within the cell. often phosphorylation of an intracellular protein. This event forms the first step in the intracellular stage of the signal transduction pathway
14.1.2. Signal transmission mediated by cell surface receptors • Many extracellular signaling compounds are unable to enter the cell because they are too hydrophilic to penetrate the lipid membrane and the cell lacks a specific transport mechanism for their uptake. • Binding of the signaling compound results in a conformational change in the receptor, inducing a biochemical event within the cell, often phosphorylation of an intracellular protein. This event forms the first step in the intracellular stage of the signal transduction pathway
Table 14.2 Cell surface receptor proteins involved in signal transmission into eukaryotic cells Receptor type Description Signals G-protein-coupled Activate intracellular G-proteins, which bind GTP Diverse: epinephrine, peptides (e.g, glucagon ). and control biochemical activities by conversion protein hormones,odorants, light of this gtP to GDP with the release of energy Tyrosine kinases Activate intracellular proteins by tyrosine Hormones(e.g, insulin), various growth factors phosphorylation Tyrosine-kinase-associated Similar to tyrosine kinase receptors but activate Hormones, growth factors intracellular proteins indirectly(e.g, see description of STATs in the text) Serine-threonine kinases Activate intracellular proteins by serine and/or Hormones, growth factors threonine phosphorylation Ion channels Control intracellular activities by regulating the Chemical stimuli (e.g, glutamate), electrical movement of ions and other small molecules charges into and out of cells
Direct activation of a st Activation via a JAK JAK P-STAT P-STAT Moves to the nucleus Moves to the nucleus and activates the and activates the target genes target genes