Intracellular compartments and protein transport with notes
Proteins Intracellular Compartments and Protein Transport
Page 1: Overview
Introduction to proteins and their roles within intracellular environments.
Page 2: Protein Sorting (Overview)
Key Components: CYTOSOL, mRNA, Ribosomes, Mitochondrion, Plasma.
Processes Involved:
Translocation
Gated transport
Endoplasmic reticulum (ER)
Nucleus
Vesicle
Peroxisome
Golgi
Extracellular Space
Secretory pathways and endocytic pathways
Page 3: Membrane-Enclosed Organelles
Function: Segregate metabolic processes in eukaryotic cells through internal membranes.
Page 4: Key Organelles and Their Functions
Nucleus: Contains genetic material and controls cellular activities.
Ribosomes: Synthesizes proteins by translating mRNA.
Rough ER: Modifies and synthesizes proteins.
Smooth ER: Synthesizes lipids, metabolizes carbohydrates, detoxifies chemicals.
Mitochondria: ATP production through cellular respiration.
Lysosomes: Contains digestive enzymes for breaking down macromolecules.
Peroxisomes: Breaks down fatty acids and detoxifies harmful substances.
Chloroplasts (in plants): Conduct photosynthesis.
Page 5: Evolution of Membrane-Enclosed Organelles
Origins:
Nucleus and ER evolved via invagination of the plasma membrane.
Mitochondria and chloroplasts derived from prokaryotes through endosymbiosis (Endosymbiont theory).
Page 6: Protein Sorting Mechanisms
Three primary mechanisms for protein import into organelles.
Page 7: Mechanisms of Import
Nuclear Pore Complex: Proteins enter the nucleus through complexes.
Vesicular Transport: Vesicles bud from one organelle to transport proteins to targets.
Membrane Transport: Proteins cross membranes via specific proteins/channels, often needing to unfold/refold.
Page 8: Signal Sequences in Protein Targeting
Normal Signal Sequence: Proteins without sequences remain in cytosol. ER proteins possess specific sequences for ER targeting.
Relocated Signal Sequence: Changes behavior when moved among proteins.
Page 9: Typical Signal Sequences
Examples of signal sequences for various organelle imports:
Import into ER: +H2N-Met-Met...
Retention in lumen of ER: -Lys-Asp...
Import into mitochondria: +H3N-Met-Leu...
Nucleus and peroxisomes also have distinct signal sequences.
Page 10: Protein Transport Mechanisms
Overview of mechanisms involved in protein transport to organelles.
Page 11: Nuclear Pore Complex
Structural Features:
Double membrane of nuclear envelope.
Proteins known as nucleoporins compose the NPC.
Page 12: Import of Nuclear Proteins
Process:
Nuclear Localization Signal (NLS) recognized by Importin proteins.
Forming complexes and docking at the NPC for transportation.
Page 13: Protein Transport via Active Transport
Energy provided by GTP hydrolysis for transport processes.
Importin recycling after cargo release.
Page 14: Protein Transport to Mitochondria and Chloroplasts
Unfolded Proteins: Synthesized with targeting signals for mitochondria.
Involves TOM and TIM translocases and chaperones for folding.
Page 15: ER Protein Synthesis & Transport Mechanisms
Discussing the extensive membrane network in eukaryotes.
Page 16: The Endoplasmic Reticulum (ER)
Rough ER: Protein synthesis; Smooth ER: Lipids, detoxification, calcium storage.
Page 17: Ribosome Function in Protein Synthesis
Translation Process: Ribosomes read mRNA and synthesize proteins, delivering amino acids.
Page 18: Targeting Ribosomes to the ER
Mechanism of ER Signal Sequence: SRP binds to sequences and pauses translation until docking with the ER occurs.
Page 19: Soluble Protein Import into the ER Lumen
Process in ER lumen during protein synthesis and folding.
Page 20: Integration of Trans-membrane Proteins
Transmembrane Protein Synthesis: Mechanisms for proteins residing in the membrane structure.
Page 21: Double-Pass Transmembrane Protein Definition
Mechanisms of internal signal sequences and translocation.
Page 22: Protein Glycosylation in the ER
Importance: Involves oligosaccharides linked to dolichol aiding in protein modification.
Page 23: Role of Chaperones
Prevent misfolded proteins from exiting the ER and assist in correct folding processes.
Page 24: Unfolded Protein Response (UPR)
Initiated in response to accumulation of misfolded proteins, enhancing folding capacities.
Page 25: Golgi Apparatus Functions
Modification and Sorting: Golgi modifies and packages proteins for their final destinations.
Page 26: Secretory Pathways
Overview of processes moving proteins to the extracellular environment.
Page 27: Protein Covalent Modifications in the ER
Disulfide bonds and oligosaccharide side chains formed during protein maturation.
Page 28: Vesicular Transport Overview
Exocytosis and Endocytosis: Mechanisms by which cells manage internal materials.
Page 29: Vesicular Transport and Budding Mechanisms
Driven by specific protein coats and targeting via signal sequences.
Page 30: Clathrin Coated Vesicle Formation
Mechanisms for vesicle formation involving cargos and clathrin assembly.
Page 31: Vesicle Docking Process
Role of Rab and tethering proteins to ensure correct attachment to target membranes.
Page 32: SNARE Proteins in Membrane Fusion
SNAREs mediate vesicle fusion through specific interactions with target membranes.
Page 33: General Mechanism of Endocytosis
Phagocytosis as a method for cellular engulfment of materials.
Page 34: Exocytosis Overview
Process for releasing secretory proteins from cells; involves docking and fusion.
Page 35: Phagocytic Mechanism
Steps detailing how phagocytic cells ingest and digest other cells.
Page 36: Endocytic Pathways
Overview of fluid and macromolecule uptake through various endocytosis methods.
Page 37: Detailed Endocytic Pathways
Investigates receptor-mediated methods that viral pathogens may utilize.
Page 38: Endocytosis Pathway of Coronavirus (SARS-CoV-2)
Mechanistic overview of viral entry, genome release, and replication.
Page 39: Mechanisms of Protein Secretion via Exocytosis
Differentiating between constitutive and regulated secretion processes.
Page 40: Lysosomal Functions
Highlighting digestion processes involving lysosomal enzymes.
Page 41: Pathways for Lysosomal Material Delivery
Autophagy, phagocytosis, and endocytosis processes detailed.
Page 42: Classical and Non-classical Secretion Pathways
Various modes of secretion highlighted in cellular environments.
Page 43: Questions?
Conclusion, inviting discussions and queries on protein transport mechanisms and pathways.