TAILIEUCHUNG - Biochemistry, 4th Edition P102

Biochemistry, 4th Edition P102. 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. | What Are the Mechanics of mRNA Translation 973 GTP Hydrolysis Fuels the Conformational Changes That Drive Ribosomal Functions Two GTPs are hydrolyzed for each amino acid residue incorporated into peptide during chain elongation one upon EF-Tu-mediated binding of aa-tRNA and one more in translocation. The role of GTP with EF-Tu as well as EF-G is mechanical in analogy with the role of ATP in driving muscle contraction see Chapter 16 . GTP binding induces conformational changes in ribosomal components that actively engage these components in the mechanics of protein synthesis subsequent GTP hydrolysis followed by GDP and Pi release relax the system back to the initial conformational state so that another turn in the cycle can take place. The energy expenditure for protein synthesis is at least four high-energy phosphoric anhydride bonds per amino acid. In addition to the two provided by GTP two from ATP are expended in amino acid activation via aminoacyl-tRNA synthesis see Figure . A DEEPER LOOK Molecular Mimicry The Structures of EF-Tu Aminoacyl-tRNA EF-G and RF-3 EF-Tu and EF-G compete for binding to ribosomes. EF-Tu has the unique capacity to recognize and bind any aminoacyl-tRNA and deliver it to the ribosome in a GTP-dependent reaction. EF-G catalyzes GTP-dependent translocation. The structure of the EF-Tu tRNA complex is remarkably similar to the structure of EF-G EF-Tu tRNA is shown on the left in the figure EF-G is in the center . The EF-Tu tRNA structure is Thermus aquaticus EF-Tu Phe-tRNAPhe complexed with GMPCP purple GMPCP is a nonhydrolyzable analog of GTP pdb id 1TTT . The EF-G structure has GDP bound purple pdb id 1DAR . Note that parts of the EF-G structure mimic the structure of the tRNA molecule. Both EF-Tu and EF-G bind to the factor-binding center which is located on the L7 L12 side of 50S ribosomal subunit. Part of this center has an associated GTPase function that plays an integral role in the binding and release of these factors. .

• Sinh học
• Nền tảng của hóa sinh học
• trao đổi chất protein
• RNA trao đổi chất
• nguyên tắc của hóa sinh
• Axit amin
• công nghệ DNA