Biochemistry, 4th Edition P106. Continuing Garrett and Grisham's innovative conceptual and organizing framework, "Essential Questions," BIOCHEMISTRY guides students through course concepts in a way that reveals the beauty and usefulness of biochemistry in the everyday world. Streamlined for increased clarity and readability, this edition also includes new photos and illustrations that show the subject matter consistently throughout the text. New end-of-chapter problems, MCAT practice questions, and the unparalleled text/media integration with the power of CengageNOW round out this exceptional package, giving you the tools you need to both master course concepts and develop critical problem-solving skills you can draw upon. | How Do Signal-Transducing Receptors Respond to the Hormonal Message 1013 SH3 SH2 PH PDZ dimer FIGURE Five of the protein modules found in cell signaling binding specificity of these modules is shown in Figure . SH3 domains bind to proline-rich peptides SH2 domains bind to phosphorylated tyrosine residues PH domains bind to phosphoinositides such as IP3 PDZ domains bind to the terminal four or five residues of a target protein pumilio domains bind to segments of RNA. A given protein may have a number of these protein modules giving it the ability to interact with multiple partners. Pumilio complexed with RNA green How Do Signal-Transducing Receptors Respond to the Hormonal Message All receptors that mediate transmembrane signaling processes fit into one of three receptor superfamilies Figure 1. The G-protein-coupled receptors see Section are integral membrane proteins with an extracellular recognition site for ligands and an intracellular recognition site for a GTP-binding protein see following discussion . 2. The single-transmembrane segment 1-TMS catalytic receptors are proteins with only a single transmembrane segment and substantial globular domains on both the extracellular and the intracellular faces of the membrane. The extracellular domain in the ligand recognition site and the intracellular catalytic domain is either a tyrosine kinase or a guanylyl cyclase. 3. Oligomeric ion channels consist of associations of protein subunits each of which contains several transmembrane segments. These oligomeric structures 1014 Chapter 32 The Reception and Transmission of Extracellular Information FIGURE a Many signaling proteins consist of combinations of protein modules each with a specific binding or enzymatic function. b Such multifunctional proteins can act as scaffolds that direct the assembly of large signaling complexes termed signalsomes. b FIGURE The membrane receptor G-protein-coupled .
