Rab作為酵素的功用

Rab proteins  like Sar a and ARF Rab proteins belong to the GTPase superfamily of switch proteins
OK so Rab is a kind of GTPase superfamily of switch proteins.
If we do not refer to the previous factors whose functions are effecting the Rab.
Then
Rab will interact with a surface protein on a particular transport vesicle and insert its isoprenoid anchor into the vesicle membrane. You should pay attention that the word-anchor.
The Rab5 and GTP add to cell free extracts accelerates the rate at which these vesicles fuse with each other.
 Besides the EEA1-early endosome antigen 1 resides on the membrane of the early endosome functions as the effector for Rab 5
 
OK  refer to the figure 17-11  the proteins shown in the example partici;ate in fusin of secretory vesicles with the plasma membrane  similar mediate all all vesicle fusion events
Rab tethered via a lipid anchor to a secretory vesicle binds to an effector protein complex and docking the transport vesicle on the appropriate target membrane v-SNARE protein  VAMP interacts with the cytosolic domains of the cognate t-SNAREs  syntaxin and SNAP-25
 
Rab GTPases control docking of besicles on target membranes
 
To analyze the problem here,
Thrombin is a specialized peptide receptor. 凝血 is it a receptor? worth to doubt.
now we compare the Human and Xenopus thrombin receptor representing their respective tethered ligand domains. the chimeric receptors techniques are used
compare two agonist peptide , evaluate the EC50 of human – SFLLRN
Xenopus agonist- TFRIFD
 
             Human whole thrombin receptor                         Xenopus thrombin receptor
 
basic sensitivity     0.2                                          0.3     for their agonist respectivity
                              10, lower sensitivity                  above 300, much lower sensitivity
                              to Xen                                         to Human agonist
 
 
 
 
 
               reserve HO domain                                  change the Amino terminus to 75
 
           sensitivity is little lower
 
bla bla bla  anyway the figure should be rearranged to a horrizontal arrangement than you can compare the difference
 
 
when we discuss about the regulation effectors those convert the Rab, they are guanine nucleotide-exchange factor(turn on ) and GTPase-accelerating protein GAP
(turn off)
 
The experimental designation     basically  an in vitro cell culture experiment   we can use the cRNA experimental technique to quench the production of active form Rab    that is    to inhibit the transcription of guanine nucleotide-exchange factor   
 

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