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IUB BIOL-L 211 - Protein Sorting and Localization

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BIOL-L211 Lecture 33 Outline of Last Lecture I. Translation ElongationII. Translation TerminationOutline of Current Lecture I. AntibioticsII. ArticleIII. Protein FoldingIV. Protein Targeting (Eukaryotes)Current LectureProtein Sorting and LocalizationI. AntibioticsA. Antibiotics are found in the environment and fight bacterial infection1. Also can target eukaryotic cellsB. Resistance has led to increased research and development of antibioticsC. Around 40% work by a mechanism that targets ribosomes and affects translationD. Puromycin Mechanism1. Inserts into A site2. Becomes a target for peptide bond formation3. Polypeptide chain is transferred to Puromycin4. No more amino acids can be added5. Truncated protein dissociates, now ineffectiveII. ArticleThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.A. "Mapping the Human Proteome" –The ScientistB. Human Protein Atlas1. Interactive database of millions of maps of around 20,000 different proteins in the body2. Data collected using fluorescently-tagged antibodies that mark proteinsa. Visualized with microscopyb. Analyzed with other techniquesC. Maps compared between healthy tissues and cancer tissuesD. Most proteins in the study are common to all cellsE. ~2000 proteins are unique to certain tissuesF. Testes have largest number of unique proteins thus far (999)III. Protein FoldingA. Recall formation of primary, secondary, tertiary, and quaternary structureB. Chaperone Proteins: promote correct protein folding1. GroEL: chaperone found in some bacteriaa. Two subunits in barrel-like structure2. GroES: additional chaperone found in some bacteriab. Forms a lid for GroELC. GroEL/GroES Mechanism1. Partially folded protein enters GroEL (barrel)2. ATP aids in binding the GroES cap to the GroEL (barrel)3. Protein is properly folded4. ATP hydrolysis releases the properly folded protein and GroESIV. Protein Targeting (Eukaryotes)A. 3 options for proteins1. Remain in cytoplasm2. Targeted for secretion3. Transported to a specific organelleB. Protein Localization Sorting Motif: like a zip code that identifies a protein's target location1. Found at N-terminus, C-terminus, or both2. Nuclear Localization Sequence:a. 5-10 basic, positively charged amino acids signal that a protein is for the nucleus3. Endoplasmic Reticulum Retention Sequencea. KDEL (Lys-Asp-Glu-Leu)b. If this sequence remains, proteins will not leave ERC. Endomembrane System: different membranes suspended in the cytoplasm1. Nuclear envelope, ER, Golgi apparatus, lysosomes, vacuoles, vesicles, and cell membrane2. Connected directly or via vesicles3. Proteins enter endomembrane system via ER (target destination with sorting motif)D. Endoplasmic Reticulum (ER)1. Continuous with nuclear envelope2. Cisternae: system of connected sacs and tubules of ER; also stacks of membranes in the Golgi apparatus3. Rough ER: has ribosomes on cytoplasmic side, and involved in protein synthesis and folding 4. Smooth ER: no ribosomes, and helps synthesize lipidsE. Targeting to ER1. Signal Recognition Particle (SRP): recognizes and binds the translated signal sequence, halting translation2. Ribosome and polypeptide brought to a receptor in ER membrane by SRP3. Once SRP leaves, translation resumes and the polypeptide enters the ER via translocation complex4. Proteins in the ER have their signal sequences removed; then are part of endomembrane systemF. The Golgi apparatus1. Modifies, sorts, and packages proteins for export (like FedEx)2. Consists of cisternae3. Proteins are incorporated into transport vesicles in the ERa. Those vesicles dock along the cis face of the Golgi apparatusb. Proteins dumped into the Golgi4. CIsternae perform protein modifications5. At trans face of Golgi, proteins packaged into membrane vesicles or secretory vesicles6. From there, they are sent to their various destinations in cell/out of


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