Identify the primary level of structure for the following pept...

Question

Identify the primary level of structure for the following peptide, which is an inhibitor of the Angiotensin I Converting Enzyme (ACE I) and a regulator of blood pressure and hypertension. Circle all the α-carbons.

Chemical structure of a peptide inhibitor of ACE I, highlighting α-carbons for primary structure identification.

Accepted Answer

So this practice problem wants us to identify the primary level of structure for the following peptide in the figure, which is actually an inhibitor of angiotensin 1 converting enzyme ACE 1 and a regulator of blood pressure and hypertension. So pretty cool. This peptide that you're looking at actually regulates our blood pressure and hypertension. And then it also says to circle all of the alpha carbons. And so notice that on the far left, what we have is our 4 mnemonics to group our 20 amino acids into their four groups. The non polar amino acids, which is Gav Limp, the aromatic amino acids, which is Fat Young Whippersnappers, the polar amino acids, which is Santa's team crafts new quilts, and then, of course, the charged amino acids which are, dragons eat knights riding horses. And so, these are gonna help us identify the R groups. And so notice over here on the far left, what we have is our amino group which is charged, and the amino group is, connected to a carbon atom, which is gonna be our first alpha carbon, and we know because it's, connected to an r group. And notice that this r group actually has a positive charge. It has a positive charge on it. And so this has to be one of our positively charged basic amino acids. And so, really, when we analyze it closely, we'll realize that this is actually arginine structure. So this is arginine. And recall that arginine really has features of the, lysine, which is the knight, and histidine, which is the sword. So, because it has features of the sword, lysine, we look at arginine's, one letter code and we think a sword you try to poke somebody with, so how many corners does the r have that you could try to poke somebody with? Really, it's got 3. So that tells us that there must be a 3 carbon start to our chain and we've got 1, 2, 3 carbons. Perfect. So we got a 3 carbon start to our chain and then it also tells us that there must be a triangular nitrogen structure. And here, we've got our triangular nitrogen structure. So perfect. This is arginine's R group. And so because this is arginine's R group, we can go ahead and put its one letter code right up here, r for arginine. So then next, what we have is our carbonyl group, which is bonded to a nitrogen and notice that the amide bonds are already highlighted in red for us. So these are the peptide bonds and those go throughout our entire, structure, which is nice. They they gave us those peptide bonds and highlighted them for us. So now, our nitrogen is going to be bonded to an alpha carbon and the alpha carbon is gonna be over here. So here's our alpha carbon because we know that the alpha carbon has to be bonded to the carbonyl group carbon, so it can't be this one because if it were this one, it wouldn't be bonded to the carbonyl group carbon. So it's got to be this, carbon here, which is the alpha carbon. And so notice that this is a cyclic r group, so our r group right here goes down and it comes back and combines right back up to the nitrogen, so we've got a cyclic r group. And so this is really gonna be proline's r group, and proline is one of our non polar amino, amino acids, p. And so really, its backbone, so notice the backbone goes like this, and its r group is like the loop of a p. And so really, that's what we're seeing with its r group. And so, what we can do is put in a p here for proline, for this amino acid. So then we've got our carbonal group, our peptide bond, and then what we have is our next alpha carbon, which is right here. And again, what we see is that we've got this proline all over again. And so, we can go ahead and put in another p here for our second proline back to back. So then we've got our next, peptide bond and then we've got our next alpha carbon, which is over here. And notice that this one's bonded to 2 hydrogens. They're not being shown, but it's bonded to 2 different hydrogens. And so that means that this must be glycine, and glycine's one letter code is just a g. So then we got our next peptide bond and our next alpha alpha carbon. And this alpha carbon, notice it's bonded to an R group and the R group has a benzene ring in it right here. So this has got to be one of our fat young whippersnappers, one of our aromatic amino acids. And when you look at it, it's really like alanine, so it's got a carbon right here and it's got the the phenyl group. So it's alanine with a phenyl group, so that must mean that it is phenylalanine. And so because this R group here is phenylalanine, we can put in an f for our next amino acid. Then we got a peptide bond and then next, what we have is our next alpha carbon. And notice that this is, our next R group, which is right here and it's got an alcohol group in it, so we're thinking, okay, well, maybe this is alcohol is a serious threat, you know, maybe it's one of the polar amino acids and indeed it is. It's actually serine, it's gonna be serine. So serine is just alanine with serine. It's gonna be serine. So serine is just alanine with an alcohol group, and that's what we've got here. So because this R group here is serine, we're gonna put s for our next amino acid. Then we have a peptide group and then we have our next alpha carbon, which again, has to be bonded to the carbonyl group carbon. So we know it's not this one, it's gotta be the one that's here. And so, again, what we've got is this circular r group that comes right back up and loops on itself. So this is gonna be proline all over again. So our next one is p for proline. So that's our 3rd proline. And so then we have our next peptide bond and our next alpha carbon, which is right here. And again, what we see is that we've got another alanine with a phenyl group attached to it. So here's a, the benzene ring, we know it's gonna be aromatic and it's just alanine with a phenyl group, we've seen it already over here, so this is just phenylalanine again. And so we're getting close to the end here, we've got our last peptide bond and our last alpha carbon. And again, what you'll notice is that this r group here really looks similar to this one over here that's because they're exactly the same. And so this is just going to be arginine all over again. So this is arginine. Here, let's put that in blue. And so what you'll notice is that we've basically identified the, sequence from the n terminal over to the c terminal, because over here, we have a free carboxyl group. And so, we've identified from the n terminal to the c terminal, and this concludes this practice problem. So I'll see see you guys in our next video.

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Identify the primary level of structure for the following peptide, which is an inhibitor of the Angiotensin I Converting Enzyme (ACE I) and a regulator of blood pressure and hypertension. Circle all the α-carbons.

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