Chapter 7

Chapter 7 - Chapter 7 Signaling Autocrine: signal to self...

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Chapter 7 Signaling Autocrine : signal to self Paracrine : signal to local neighbors Hormones : signal over great distance Signal transduction pathway – a ligand (signaling molecule) binds to the receptor , leading to a pathway Lac operon in bacteria: when lactose is present, three continuous structural genes are transcribed along with the promotor and operator Bacterial response due to osmotic pressure (omp): EnvZ protein acts as a kinase to phosphorylate itself, transfering the phosphate to the OmpR protein, which changes shape and starts the transcription of OmpC gene responsible for closing pores in the outer membrane, preventing additional solute intake Nonpolar signals (ei: ethylene, steroid) can cross the plasma membrane and bind to receptors in the cytoplasm Polar signals (ei: epinephrine, large peptide) bind to receptors in the cell membrane Receptors in the cytoplasm or embedded in the plasma membrane Inhibitors can also bind to these Receptor proteins undergo temporary conformational change when specific ligands bind Cytoplasmic steroid receptors: in the absence of the steroid, the receptor is bound to a chaperone ; with a steroid, the receptor can enter the nucleus 3 receptors, all involving amplification : Ligand-gated ion channels : acetylcholine (ACh) receptor … ACh on muscle cells opens the receptor and allows Na+ to rush inside, depolarizing the cell Protein kinases : such as the insulin receptor … insulin binds outside and opens the receptor’s cytoplasmic protein kinase active site, phosphorylazing itself and specific cytoplasmic proteins which can insert glucose transporters into the plasma membrane; active Ras protein caused cancer by phosphorylating MAPk, which enters the nucleus and triggers mitosis G protein-linked receptors : many receptors have seven membrane spanning
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Chapter 7 - Chapter 7 Signaling Autocrine: signal to self...

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