BIOL 3510 1st Edition Lecture 16 Outline of Last Lecture I. Parts of the ChloroplastII. PhotosystemsIII. Charge SeparationIV. Noncyclic PhotophosphorylationV. Carbon Fixation in the StromaVI. Uses of Glyceraldehyde 3-phophateOutline of Current Lecture I. OrganellesII. Mechanisms of Protein Transport into OrganellesIII. PeroxisomesCurrent LectureCells contain many membrane-enclosed organelles. Organelles perform diverse functions:- Cytosol: metabolic pathways, protein synthesis- Nucleus: contains nuclear genome, DNA and RNA synthesis- Mitochondria: ATP synthesis by oxidative phosphorylation- Chloroplasts: ATP synthesis and carbon fixation by photosynthesis- Endoplasmic reticulum (ER): membrane synthesis, protein distributiono Rough ER: ribosomes attachedo Smooth ER: Ca 2+ sequestration etc.- Golgi apparatus: proteins and lipid modification and sorting- Lysosomes: intracellular degradation- Endosomes: sorting of endocytosed material- Peroxisomes: oxidation of toxic moleculesThree Mechanisms of Protein Transport into Organelles1. Transport through nuclear pore: folded proteins enter through nuclear pores2. Transport across membrane: unfolded proteins enter organells via protein translocators3. Transport by vesicles: folded proteins move via transport vesicles that fuse with destination membranesThese 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.Folded proteins with nuclear localization signals (NLS) are bound by import receptors.Nuclear import receptors and cargo cross the nuclear envelope via the nuclear pore.Ran-GTP binds to the nuclear import receptor in the nucleus and returns it to the cytoplasm. Ran-GAP (GTPase activating protein) and RAN-GEF (guanine exchange factor) mediate the activity of Ran.Unfolded proteins enter mitochondria (and chloroplasts) via protein translocators.Chaparones that bind unfolded proteins and hydrolyze ATP drive import into the mitochondria.Peroxisomes- Contain oxidative enzymes- Use O2 and H2O2 to remove protons- Break down fatty acids- Involved in the formation of plasmalogen, a phopholipid needed for neuron function- Import proteins via the action of peroxins that use ATP as n energy source, exact mechanism is unclearRough ER contains bound ribosomes. When translating proteins with ER signal sequences, ribosomes aretargeted to the ER.ER protein targeting depends on the interaction between the signal recognition particle (SRP) and the SRP receptor. ER proteins are threaded through a protein translocator.After signal sequence cleavage, soluble proteins are released into the ER lumen.The arrangement of ER membrane proteins is determined by hydrophobic start transfer and stop transfer sequences.The location of positively charged amino acids determines the orientation of protein insertion- Before the start-transfer: N terminus is cytosolic- After the start-transfer: N terminus is
View Full Document
Unlocking...