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vacuole

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vacuole

Postby kea160 » Sun Sep 09, 2007 5:38 pm

i am supposed to make the connection between structure and function. the question is what structure tells the vacuole to dock where it needs to?
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Postby MrMistery » Sun Sep 09, 2007 6:17 pm

None. Because vacuoles do not dock. You(or your teacher) are a bit confused about the difference between a vacuole and a vesicle.
A vacuole is the equivalent that plant cells have to lysosomes. Usually a plant cell has only one large, central vacuole.
A vesicle is what you are referring to. Vesicles are used to transport various proteins and lipids between the members of the endomembrane system and to the plasma membrane.

Now. What tells a vesicle to dock where it needs to? Unfortunately there is no easy answer to this. Generally speaking, the system works on proteins complementary in structure like a lock and a key. One protein is on the vesicle, the other is on its target(for example: on the Cis-Golgi). Now exactly what proteins are used really depends on where that particular vesicle is going. The two most common protein families used for this purpose are the SNARE proteins and the Rab proteins. But like I said, it depends.

Hope this sheds some light on the subject
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Postby Darby » Wed Sep 12, 2007 1:40 am

I've never run into such a functional distinction between vesicles and vacuoles.

Anyway, I'm guessing that microfilaments contribute to their movement in the cells, since they exist in cells that don't have active microtubules, and that fusion with other membranes involves recognition molecules and maybe clathrin.
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Postby MrMistery » Thu Sep 13, 2007 5:28 am

clathrin doesn't have anything to do with the docking of a vesicle. Clathrin is the protein that, by assembling into a closed cage of triskelions, is able to create a vesicle from the parent membrane(well, it's not actually that easy, cause molecules like dinamin are needed to pinch off the vesicle). After the vesicle has formed, the clathrin coat is dissasembled by the SAR and ARF proteins that directed its formation. this is important, because it exposes binding molecules like v-SNARE
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Postby Darby » Sun Sep 16, 2007 12:06 am

Has the role of clathrin in internal systems really been studied, though? Say, in Golgi systems-?
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Postby MrMistery » Sun Sep 16, 2007 11:16 am

aaah.. yeah. I didn't just make that up you know. From what i know, it is fully(or almost fully) understood. Here is a nice animation presenting a model of the clathrin coat assembly. From MBOC
http://files-upload.com/files/505913/clathrin.mov
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