Introduction to Molecular and Cell Biology, Biol. 220 Lecture 20: Transcription Regulation
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Molecules are directed to specific target vessicles by modification or aggregation of these molecules with specific transmembrane proteins in the target vessicles.

• Carbohydrates attached to lysososomal bound proteins are phosphorylated (Fig. 17.39).
• Fig. 17.39
  

• Phophorylated proteins are attached to membrane bound proteins which have lysosomal targeting alpha domain (Fig. 17.40).
  Fig. 17.40
  
  
  
• Regulated vessicles have  specific secretory proteins that aggregates and targets vessicles to be regulated (HyperCell movie).
  
  
• Localization of transmembrane vessicles to apical or basal membranes is controlled by the presence of the transmembrane proteins Rab and V-SNARE (Fig. 17.43)

Pro-proteins are cleaved into active proteins late in the secretion process (Fig. 17.42).

Fig. 17.42

At least three types of coated vessicles transport proteins from organelle to organelle (Fig. 17.50).

Fig. 17.50

• Clathrin                      golgi to lysosomes and plasma membrane and endocytosis (Fig. 17.53).
• Coatamer I (COPI)      golgi to ER   (Fig. 17.58).
• Coatamer II (COPII)   ER to golgi
  Fig. 17.53
  
  Fig. 17.58
  
  

Adapter proteins bind between coat protein and the vessicle membrane.
Dynamin completes the pinching off of the clathrin coated vessicle (Fig 17.54).

Fig. 17.54

Depolymerization (by cytosolic Hsc 70) of the clathrin and coatamer exposes transmembrane proteins (V-SNARE) that direct the vessicle to its destination by binding to the specific T-SNARE protein on the target organelle.  The fusion protein SNAP25 causes the vessicle to fuse with the target membrane (Fig. 17.59)

Fig. 17.59

 

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