Quaternary Protein Structure - Video Tutorials & Practice Problems

Quaternary Protein Structure Concept 1

Now, the Quain structure of protein is its highest level of complexity. We're going to say it results from the interaction between our side chains of two or more subunits. Now what exactly is a subunit? Well, a subunit is an individual polypeptide chain possessing a tertiary structure. So that means that it comes with it all the types of interactions that are normal for tertiary structure such as hydrophobic, hydrophilic, uh hydrogen bonding, all these different types of interactions that we see within a tertiary structure would carry over the Quain structure. Now, here we also have what's called a multi meric protein. This is a fully functional protein that possesses multiple subunits. Now, with a multi meric protein, we can have terms such as dimer trimmer and heer dimer means that we have two subunits together trimmer means we have three subunits and tetramer means we have four subunits. Here, we've done a huge journey from our primary structure all the way now to our quaternary structure. Remember, our primary structure has a sequence of amino acids connected to each other through peptide bonds. It then translates into two repeating patterns which create our secondary structures. So we have our alpha helix and our beta plated sheets. These happen on the same chain. So different portions of the chain can create alpha helices or beta plated sheets. From there, we get to tertiary structures where hydrophobic interactions kind of cause the chain to fold in on itself, creating even further interactions. So here we'd have our folded peptide. Now, if enough of these start coming together, we can have dimers trimmers and tetramers. In this example, here we have one, 234 subunits interacting with one another coming together to help give us our quaternary structure. In this case, we'd say that this is a functional protein. Now, you might also notice that within this image, we have these little spheres which we did not have in our tertiary structure with Quain structures. Sometimes we also have the addition of what's called a prosthetic group. This is basically a non amino acid component that forms a part of the quaternary structure of a protein. Right. So here in this image, we have our four subunits. And in addition to this, we have four prosthetic groups together. This helps to make a functional protein just for reference. This is an example of hemoglobin, a very popular Quain structure for a protein. And those prosthetic groups are heme groups which help to carry iron. Remember, this helps us carry iron within our cells in order to help us basically maintain our metabolism and keep us going as human beings Right. So remember we talk about going from primary all the way to quandary, it becomes more and more complex and this is what we're seeing when it comes to this image.

Quaternary Protein Structure Example 1

Which of the following is our true for the protein structure of an E coli sample, right? So if we take a look here, we can see that in this E coli sample, we have what we have three tertiary structures, right? So we have three different peptide chains, all coalescing all coming together to form this structure. Now because we have two or more sub units, each one of them representing a sub unit. We know that we have a Quain structure. All of them are saying that but there are three of them. So that would mean that it is a trimmer or trimeric. We look at our options, not dyer. So that's out not tetra meric because that's not 43, not monomer, it's not one, it BD because here it's a Quain structure that which is trimeric because it's three tertiary structure chains or three subunits and they're held together by non covalent bonds. That is true. In this case, they're not covalent bonded to each other, they connected to each other through non covalent means. So here option D would be the best choice. It's Quain area. Yes. And it's the only one that says Primary.

Hemoglobin represents a commonly discussed tetramer that contains an even number of α and β subunits. Which of the following statements is true?

• A. Hemoglobin must contain with 4 α subunits and 4 β subunits.
• B. Hemoglobin must contain with 2 α subunits and 2 β subunits. 
• C. Hemoglobin contains R groups that only covalently bind to produce a quaternary structure. 
• D. Hemoglobin represents a multimeric protein with identical subunits.

Which of the following could be classified as a prosthetic group?

• A. I only 
• B. I, III, IV
• C. II only 
• D. II, IV
• E. None of the above

Which of the following correctly orders the protein structural terms from lowest to highest complexity?

• A. Peptide Bond < Primary structure < 2 subunits < Secondary structure < tetramer < Tertiary structure.
• B. Primary structure < Peptide Bond < Secondary structure < 2 subunits < Tertiary Structure < tetramer.
• C. Peptide Bond < Primary structure < Secondary structure < Tertiary structure < 2 subunits < tetramer.
• D. Peptide Bond < Primary Structure < Secondary structure < 2 subunits < Tertiary structure < tetramer.