341lecture27nov16sakai - Cell Biology 341 Last lecture:...

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Cell Biology 341 Monday, November 16, 2009 Today: • Sorting from the Golgi apparatus • The signal for sorting to the Last lecture: • Coat proteins on the cytosolic surface of a vesicle help shape the vesicle and select its cargo and v-SNAREs • Coat-recruitment GTPases (Sar1 or Arf) recruit adaptors and outer coat proteins to form a vesicle → dynamin pinch lysosomes is a P-sugar • Endocytosis • Begin Chapter 14 on how mitochondria produce ATP • Adaptors bind cargo receptors and membrane cargo proteins • Rab GTPase proteins target vesicles to the correct destination membrane → SNARE coupling • See figure 13-5 for coated vesicle traffic map
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The Golgi apparatus sorts proteins to the correct destination • Soluble proteins that are “resident” to the ER contain an ER retention signal of 4 amino acids at the carboxyl-terminus of the protein (KDEL, see table 12-3) • If these proteins “escape” the ER in a COPII vesicle, they are bound by the KDEL receptor in the cis Golgi, and then returned to the ER in COPI • Clathrin-coated vesicles bud from the trans Golgi, carrying soluble and membrane proteins to the endosomes • As an early endosome collects materials, it matures into a late endosome, and finally fuses with a vesicles • These are retrograde COPI vesicles, retrieving ER proteins and v-SNARES • COPI vesicles also carry proteins from the trans Golgi to the plasma membrane for secretion (soluble proteins), or to become part of the plasma membrane (default pathway) finally fuses with a lysosome • Lysosomes are digestive organelles that contain acid hydrolases which require a low pH for activity • The interior of a lysosome is maintained at pH 4.5-5.0 by a V-type ATPase that pumps H + into the lumen
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341lecture27nov16sakai - Cell Biology 341 Last lecture:...

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