13. Intracellular Protein Transport
Vesicular Budding, Transport, and Coat Proteins
13. Intracellular Protein Transport
Vesicular Budding, Transport, and Coat Proteins
1
concept
Overview
1m
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Hi in this video we're gonna be talking about vesicles budding transport and coats. So this is gonna be really just short video of an overview of what I'm even talking about when I talk about bicycle transport and budding. So transport vesicles are a little tiny membrane enclosed organelles that move molecules between organelles and the plasma membrane. And so there are two main pathways here that we're going to talk about and each one has a different mechanism and different proteins that work in them. So the first thing I want to talk about is the secret ori pathway. So that's going to be um you can think of this as secretions of things getting out of the cell. So this is going to begin internally in the cell. So it begins in the er moves through the golgi but ends at the cell surface. So this is c creating something The Secretary pathway. Then you have the an acidic pathway which is kind of the entrance pathway. And so this pathway is going to begin at the plasma membrane to the surface of the cell and it's going to bring all those molecules in and those will get started and they can go anywhere in the south. So they can go to the end zone life zone golgi er nucleus wherever they need to go. But they have to enter and they do that through the end acidic pathway. So short video. But these are the two pathways and then um we will get more into specifics later. So here we have some vesicles some are being transported out. So through here the Secretary vesicles they're leaving, they're being secreted. But then you have the alternate pathway of something potentially coming in and traveling through the golgi maybe and then through the er and then maybe even to the nucleus if it decides, and that's going to be the end acidic pathway of entrance. So with that let's get more into the specifics and move on.
2
concept
Vesicular Coats
7m
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Okay so now we're going to talk about vesicles coats. And so what I mean with the vesicles coat is exactly what it sounds like. So when we go outside we put on a coat because we're cold. Well vesicles they put on their coats but their coats are actually proteins. And so this happens most of the time. Not all the time but the majority of the time vesicles when they butt off of organelles or the plasma membrane or wherever they're going they need to be protected by that by a protein coat and that helps direct them to the proper place and helps them form and it helps them do everything they need to do to transport materials. So there are three types of testicle coats. These are all three proteins. The first is going to be classroom coated vesicles and these travel between the Golgi and the plasma membrane. Then you have the cop one and cop to which each transport through different place. So cop one does goldie towards er and cop two is um buds from the er So you'll you'll also notice if you kind of think about positionings of the cells that if it buds from the golgi towards the er that's actually gonna be inwards movement whereas buds from the er that's going to be outward move back. Um And so these are the three main protein codes that transport things throughout the cell. So what it might look like is you have all these different things that need to get inside these stars. They bind to receptors on the plasma membrane and then you have protein coats here that cause help form that bicycle And eventually this coat protein is surrounding the entire vesicles. These little red things here are the protein um and that helps the bicycle form and transport to the proper location. Now, one of the main ones that we're going to talk about is the cloth coat. And that's because classroom coats are extremely important in driving vesicles formation. So these are kind of the instigators, especially at the plasma membrane. So how this happens is there's actually these proteins called adaptor proteins and these bind both the classroom and the trans membrane proteins that are being transported. So the important thing here is that classroom isn't actually binding to anything that it's transporting. Classroom is just acting as the coat. It's not you know, interacting with particular proteins, it's not interacting with anything that it needs to get in, it's just acting as a coat, so it's just coming on. But how it connects to those things that need to get inside the cell are through adaptor proteins. So classroom binds the adaptor proteins and the adapter proteins are the ones that are specific for things that need to get in. And so one of the things that cargo or that adapter proteins bind are things like cargo receptors. And so sometimes the vesicles needs to transport soluble molecules. So these are things that are just kind of floating outside of the cell or in a certain testicle or wherever it is we'll just say outside of the cell. So there's a molecule that needs to get inside, it needs to be transported but it's just kind of floating out there. Well it's got to somehow interact with the membrane so it can get into the vesicles. So it does that through binding cargo receptors. And then those cargo receptors bind adaptor proteins which then go and bind Catherine. So once all of these interactions have taken place and the vesicles ready to bud. What you get is this other protein Dina men and this you can kind of think of I guess a ring. So it comes in and it symbols a ring around the neck and it uses the energy from G. D. P. And just pinches it off. So what this looks like here. So you have some type of soluble cargo and it needs to bind to its cargo receptor. Once it's here you have an adapter protein come in so you have your receptor your cargo and your adapter and the classroom is gonna come in and it's gonna bind the adapter. Then once you have enough of these formed then the vesicles starts budding. So you have your classroom coat here, you have your adapter here, you have your receptor here and you have your soluble um thing here. So if you want to think of it it's kind of like cars. Right? So you have your classroom, let me actually write this down here are s you have your classroom, you have your adapter. Okay, can't spell for anything. Oh my goodness. A D A V E T O R. You have your receptor and you have your soul valuable cargo cars. So then this eventually forms into a testicle and the dino men will come in right here and it'll pinch that off so that it actually forms this vesicles that can be transported anywhere in the cell. So remember cars. Um and that's with Catherine. So um obviously this needs to be regulated. Everything in the sound needs to be regulated. So how it's regulated or through GTP Aces which regulate the recruitment of the coats. So obviously vesicles won't form without the coat. So if the coats never get there then they won't form those things won't be transported. So GTP Aces sort of regulate this process by controlling whether or not the coats gets the membrane. So when a coat protein comes to the membrane and it binds to an adapter, this triggers this transition so G. D. P. Goes to G. T. P. Then once GTP is activated that assembles more coat proteins to the to the area. Once those coat proteins are here rab proteins are the GPS is um that are responsible for controlling the specificity. So the coat proteins that arrive they are all going to be the same type of coat protein because these GPS is um control which coat proteins can get there And so um yeah so each testicle has a different combination of rab proteins and each one of those controls which coat gets there and then once the coat gets there it changes the G. T. P. And that GTP sort of recruits all these all the same coat. So we see all these different rap proteins. So here early in the zone has wrapped five, here's a wrap seven. Now you don't need to remember these rap numbers but know that all of these that I've circled, these are different rab proteins and so each one is a different GPS wraps are GTP aces and they recruit different um coat proteins. So if the coat protein that's going to be recruited here is going to be different than the one that's here and the one that's here and this one as well. And so the specificity of the coat protein that's recruited is entirely controlled by these rab Gps is so these are kind of like the bouncers, you know, they say you are allowed to come and you're not. So that's the rab proteins. So with that let's move on
3
concept
SNARE Proteins
3m
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okay in this video we are going to focus on snare proteins and these are super important proteins for vesicles fusion. So um snare proteins are the proteins that allow the vesicles fuse because you can kind of imagine that it's not exactly easy for membranes to fuse First they have to get to the location, then they have to actually get close enough to fuse snare proteins help in both getting close enough for membrane fusion to occur and also providing specificity. You don't just want the first thing the vestibule runs into to have it fused with that you want to diffuse where it needs to go. So snare proteins to have these two functions to allow them to catalyze that membrane fusion and also to provide specificity. So there are two types of stairs which reside within the membrane. So you have T snares. So these are 2 to 3 target snares and they reside on the target organelles. So if a vestibule needs to get to the golgi there's T snares that are specific for the golgi. If the vestibule needs to get to the er then there are T snares that are specific for the er So this is where the specificity comes in. Then you have a V. Snare and this is the protein that resides on the vesicles itself. And so this V snare is like searching out the matching T stairs so that it can find which one it's supposed to bind to and help that fusion once those two snares meet. So once the proper V snare meets the property snare then they're like okay awesome, we're together you know we're going to stay together and so they actually come together to form this four helix bundle. So remember there are 2 to 3 here, one here so that's gonna equal four as long as this is three but it forms this um bundle that's really tightly bound to each other and this tight bound nous results in the vestibule fusion together so they just get so wrapped around each other and so tight that the vesicles really can't escape. So the only thing that it's going to do is it's gonna fuse. And so um after it fuses you still have the snares bound together. So what you have to do is you actually have to have energy come in and break them apart. So that energy that comes in and breaks them apart is A. T. P. And there's this special factor called the NSF. Here's the long word for it but don't worry about that NSF. Um And that uses http hydraulic sis to release the Vnt snares. So this is an important vocab word to know when it comes to stare proteins. So what we see here is we have we have our bicycle, we have our one V snare and we have our target organ al here so you can see there's the you know different three T snares and these form this four helix so 1234 helix bundle which eventually results in vesicles fusion. And so that's how snare proteins work and that's how vesicles have their specificity and um are targeted to specific organelles and what allows them to use. So they're really important. So with that let's move on.
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Problem
ProblemWhich of the following is not a protein coat?
A
COPI
B
COPII
C
COPIII
D
Clathrin
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Problem
ProblemWhich of the following coats is used on vesicles that transport molecules from the Golgi to the ER?
A
COPI
B
COPII
C
COPIII
D
Clathrin
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Problem
ProblemVesicle fusion requires all but which of the following?
A
T SNARES
B
V SNARES
C
Trans SNARE complex
D
Rab GTP proteins