Hi in this video we're gonna talk about protein sorting. So first there are three mechanisms through which proteins are sorted called gated transport. Trans membrane transport invest ical transport. So we're going to go over each one of these individually but they all have similar components and that are sorting signals. So what are sorting signals? They are short amino acid sequences located on the protein that direct the protein two different regions of the cell or different organisms. Now. One or did not different organisms, different organelles. And so once that protein with the sorting signal say an E. R. Sorting signal or golgi sorting signal or plasma membrane sorting signal, once that protein gets to its correct place, there are enzymes called signal peptide basis that actually remove that signal and leaves the protein there. And so if the protein doesn't have any sorting signals at all, it's actually left in the side of saul. So in this video let's first go over the first type of transport and that's gated transport. So gay to transport is going to refer to the transport of proteins between the side of saul and nucleus. And so the nuclear pore is responsible for this type of transport. So what happens is the nuclear pore extends to the nuclear envelope And this internal poor has all of these unstructured regions and that prevent large molecules and molecules that shouldn't get into the nucleus from passing through. And so proteins that need to get into the nucleus contain nuclear localization signals. And so this signal is actually recognized by import receptors And when that signals recognized by that receptor, it helps that protein move through the pore and it uses energy from GTP to allow that to happen. So here we have the nuclear pore. Here's an example of it. It has all these different regions that are unstructured and so normally it blocks things from getting through. But if a protein comes along and it has what's known as a nuclear localization signal in LS, it can then travel a bind to different receptors and travel through the nucleus in order to or travel through the nuclear envelope in order to reach the nucleus. So that's gated transport. Let's not move on.

So in this video we're going to talk about trans membrane transport which occurs through what are known as protein trans locators. So protein trans locators are proteins that trans locate which makes complete sense proteins across different types of organ l membranes. So typically trans locators were to trans locate a protein from the side of salt into membranes like the er mitochondria or chloroplasts. And so in order to pass proteins actually in order to pass these trans locators, proteins actually have to unfold. Um and then that trans locator can transport them across so they're directed here. Very similarly they have signal sequences that direct them to this organ al into these trans locators and then I'm usually the on the inside of the organ L you know, this unfolded protein so it now needs to be folded. So typically there are chaperone proteins that are present within the organ L. Itself and that help fold that protein again once it is trans located across. So here we have the mitochondria, this is mido and we have our trans locator here. And so we have this protein with this signal sequences the mido signal sequence and it is unfolded and passed into the mitochondria. The signal sequence is removed and then chaperone proteins come in and help re fold this protein back up into its normal form so that's protein translocation. Let's not move on

Okay so now we're going to talk about vesicles transport and vesicles transport. We're going to talk about through transport vesicles. Now what transport vesicles are. They're just really small membrane enclosed compartments that transport things and proteins throughout the cell. So how transport vesicles form and how they end up fusing is they actually pinch off in one compartment. Say the endo plasma particular. Um And then when they get to the play where they're going to end up wherever they're transporting something they're gonna fuse with that other membrane. So let's say there's a protein it's being synthesized in the er but that protein isn't meant for the er it's meant for the plasma membrane. Well what would happen is after that protein to synthesize a it's going to be in the membrane or attached somehow to the membrane so that it's incorporated into the vesicles. All right then it's going to pinch off. I didn't do that right, there we go. It's gonna pinch off. Now we have our little protein here attached to the vesicles and make it red so you can see it. And what we get is we get a vesicles here it's gonna be double membrane and we have our little protein. Now that protein can go on and travel anywhere else in the cell. And when it gets there this membrane is going to fuse with whatever compartment it's trying to release this protein into. So it can be the er to the plasma membrane. It can be the gold G. To the E. R. It can be I don't know anywhere to the mitochondria like any type of transport that can happen into or out of the cell is really transported via transport vesicles. Now inside of a transport vesicles. That environment can be very different depending on the transport vesicles. So it can differ from vesicles vesicles. It also can differ from the cida plaza. So you can have a real high concentration of a protein or a molecule. Innovest ical and a very low concentration of it outside of the testicle. You can have three vesicles each with different proteins going to different places. So the content of a vest ical is really just so independent of other vesicles in the cytoplasm itself and it can really hold most proteins and molecules. So anything soluble insoluble membrane attached can be transported this way. So you can imagine how important this type of transport is for the entire cell. So let's look at a picture of what this looks like. We have our nucleus, we have our E. R. Here and you can see that there's some type of protein that's been made this screen purple protein here and it needs to get to the plasma membrane which we can see it up here is where it ends up. So what happens is the vesicles buds off the er and we can see it here and then goes into the golgi and you can see this protein traveling through the Golgi. There's actually a couple of different ways this can travel through the Golgi but that's not for this video. We'll talk about that in another video. But one of the ways potentially it could transport is through vesicles. Um So that is a possibility here. But once it gets to the to the trans face of the golgi, instead of going to butt off into another vesicles and then make its way to the plasma membrane where that membrane is gonna fuse with the plasma membrane. And then we finally have this protein where it's supposed to be, which is in the plasma membrane. So that is vesicular transport. The transport vesicles with that. Let's turn the page.