TAILIEUCHUNG - Biochemistry, 4th Edition P97

Biochemistry, 4th Edition P97. 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 Is Transcription Regulated in Prokaryotes 923 protein protein interactions are an essential component of transcriptional activation. We see this latter feature in the activation of RNA polymerase by CAP- cAMP 2 for example. Third the regulator proteins receive cues that signal the status of the environment for example Trp lactose cAMP and act to communicate this information to the genome typically via the medium of conformational changes and DNA pro-tein interactions. Proteins That Activate Transcription Work Through Protein Protein Contacts with RNA Polymerase Although transcriptional control is governed by a variety of mechanisms an underlying principle of transcriptional activation has emerged. Transcriptional activation can take place when a transcriptional activator protein such as CAP- cAMP 2 bound to DNA makes protein protein contacts with RNA polymerase and the degree of transcriptional activation is proportional to the strength of the protein protein interaction. Generally speaking a nucleotide sequence that provides a binding site for a DNA-binding protein can serve as an activator site if the DNA-binding protein bound there can interact with promoter-bound RNA polymerase. These interactions can involve either the a- 8- J - or c-subunits of RNA polymerase. Moreover if the DNA-bound transcriptional activator makes contacts with two different components of RNA polymerase a synergistic effect takes place such that transcription is markedly elevated. Thus transcriptional activation at specific genes relies on the presence of one or more activator sites where one or more transcriptional activator proteins can bind and make contacts with RNA polymerase bound at the promoter of the gene. Indeed transcriptional activators may facilitate the recruitment and binding of RNA polymerase to the promoter. This general principle applies to transcriptional activation in both prokaryotic and eukaryotic cells. In eukaryotes transcriptional activators typically have

• 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