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Cell Biology

Learn the toughest concepts covered in Cell Biology with step-by-step video tutorials and practice problems by world-class tutors

6. Proteins

Complex Protein Structures



Complex Protein Structures

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Okay, so in this topic we're gonna be talking about complex protein structures. So proteins can form these very large complex structures that interact with other proteins and other molecules. And so I want to spend some time talking about how that happened. So um in order for proteins to form a bunch of different complex um functions. How do they actually interact with each other? Well typically they interact through things called binding site, which are just regions of the polyp peptide chain that have sequences that allow them to interact with other polyp peptide chains or larger proteins and complexes. And so um these binding sites allow for these polyp peptide chains to come together interact with each other and form multi protein protein complexes. And these multi protein complexes generally contain multi poly peptide chains. And each one of these chains usually has some kind of different function even if it's a slight difference, it doesn't have to be a huge difference but usually there's some kind of different function related to it. And these structures are dynamic. They can assemble and disassemble in response to different kind of extra extraneous signals, cellular signals. Um And so examples of these big multi protein complexes are things that we've talked about, we're going to talk about in the future and include protein complexes involved in DNA synthesis, RNA processing and a teepee creation. So um these multi com protein complexes have to be stabilized in some way. And so we've talked about this type of bond before. So do you remember what type of bond it is? And this is the bond that really it's a cold violent bond and it's really responsible for stabilizing protein complexes or poly peptide chains together. Right so these bonds are called di sulfide. They sold five bonds. These are co valent bonds that really stabilize protein structures and polly peptide chains. But it's really the only covalin bond that's involved. All the other bonds that form all the different structures that proteins can have are non covalin bonds. And those are the ones that link the polyp peptide chains together. So for to look at what a complex or multi protein complex might look like. This is an X. Zone protein is made up of six proteins each of them. You can see here in a different color 123456. And these protein complexes you know come together interact on compassionately or through di sulfide bonds to form these multi protein complexes. Now, proteins and multi protein complexes can form really complex shapes. So a couple of the shapes that they can form are things like Hella sees which is really common. A helix is a really common shape because um it's the most energetically favorable way to link sort of repetitive subunits together. So helix is a very common one. They can have sort of these elongated fibers shapes. Um You can kind of think of fibers the sort of like mesh work of sort of like springy but strong substance. Um And we find these a lot and skin or the extra cellular matrix. They can form these compact globular shapes. Um They can have unstructured regions that provide flexibility. Um and they can co violently cross links to create mesh works for instance approaching called elastin, which is really important in skin. So we're going to look at, you know, all the different ways that protein skin form. You can see that can be all different sizes from this little tiny guy here to this big honker here. Um And they have all different shapes, sort of linear shape, circular shapes, globular shapes. And um all these different protein shapes can form using multi protein complexes of multiple polyp peptide chains. So now let's move on.

What type of bonds hold polypeptide chains together to form complex proteins?


Due to the number of polypeptide chains, multiple protein complexes can only have a singular, globular shape.