The major component of the antibiotic ointment bacitracin is...

The major component of the antibiotic ointment bacitracin is a cyclic polypeptide called bacitracin A. It was first isolated in 1943 from a knee scrape from a girl named Margaret Tracy, after whom it is named. Bacitracin is effective topically and is used to treat skin, eye, and wound infections. Figure $\mathrm{P} 20.4$ shows the structure of bacitracin A. Identify the amino acids found in human proteins that are also part of the structure of bacitracin A. (FIGURE CAN'T COPY)

The major component of the antibiotic ointment bacitracin is a cyclic polypeptide called bacitracin
A. It was first isolated in 1943 from a knee scrape from
a girl named Margaret Tracy, after whom it is named. Bacitracin is effective topically and is used to treat skin, eye, and wound infections. Figure $\mathrm{P} 20.4$ shows the structure of bacitracin A. Identify the amino acids found in human proteins that are also part of the structure of bacitracin A.
(FIGURE CAN'T COPY)

Key Concepts

Structure–Activity Relationships in Antibiotics

Structure–activity relationships involve the analysis of how the molecular structure of a compound, such as a cyclic polypeptide, corresponds to its biological activity. In the context of peptide-based antibiotics, understanding which amino acids are present and how they are configured (e.g., in a cyclic structure) can provide insights into the drug's mechanism of action, specificity, and potential therapeutic applications.

Amino Acids

Amino acids are the fundamental building blocks of proteins and are used in countless biological processes. In human proteins, 20 standard amino acids are linked by peptide bonds to form diverse structures and functions ranging from enzymes to structural proteins. Understanding their structure, function, and properties is central to biochemistry and protein chemistry.

Peptide Bonds and Polypeptides

Peptide bonds are covalent chemical bonds that link amino acids together to form polypeptides. The sequential linkage of amino acids, whether in linear chains or cyclic forms, determines the three-dimensional structure and function of proteins. This concept forms the basis of understanding protein and peptide structure in molecular biology.

Cyclic Peptides

Cyclic peptides are a subset of peptides in which the amino acid chain forms a ring structure, rather than a linear chain. This cyclic configuration often confers extra stability and can enhance biological activity, which is why many antibiotic compounds employ a cyclic peptide structure to improve their function and resistance to degradation.

Transcript

00:01 So we want to see if we can identify the amino acids that are found in human proteins that are also found in this huge molecule, basitracin.

00:13 And the way to do that is to try to pick apart the peptide bonds.

00:20 And so, for example, we've got a peptide bond right here.

00:27 We don't have any naturally occurring amino acids that have this ring.

00:36 We do have one histidine that has a nitrogen where that sulfur is, but that is not a naturally occurring amino acid in humans.

00:46 Now, the next peptide bond that i would find would be here.

00:54 And so here's our alpha carbon here, our amino and our carboxylates on either side.

01:08 And here's our side chain then.

01:11 One, two, three, a four carbon side chain.

01:16 That is loosing.

01:29 And then our next peptide bond would be here.

01:35 And again our alpha carbon here and the amino on one side and the carboxylate on the other.

01:43 And then we have our side chain here with two ch2s ending in a carboxylate that is glutamate.

01:54 And then our next peptide bond would be here.

01:58 And the next alpha carbon would be there, nit amino and carboxicar on either side.

02:06 Here is our side chain, which looks very similar.

02:12 What is the difference? the difference is, that is to lucine.

02:17 The difference is that the branch here, so this is our beta number two, so to speak, and the branching is at gamma there.

02:32 And here the branching is at beta.

02:34 That is is is is is is is is is is is is is is is.

02:35 I -lucine, i -l -e.

02:42 And then our next peptide bond is here.

02:47 Here's our alpha carbon.

02:50 And again, as always, what were the carboxyl and amino groups of the original amino acid? so now our side chain looks like this.

03:03 And that is not easily recognizable.

03:13 But let's see what we get when we come around the other way...

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