Textbook Question
What kind of bond would you expect between the side chains of the following amino acids?
b. Alanine and leucine
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18. Amino Acids and Proteins
Tertiary Protein Structure
Problem 99
Textbook Question
Oxytocin is a small peptide that is used to induce labor by causing contractions in uterine walls. It has the primary structure Cys-Tyr-Ile-Gln-Asn-Cys-Pro-Leu-Gln. This peptide is held in a cyclic configuration by a disulfide bridge. Draw a diagram of oxytocin, showing the disulfide bridge.
Verified step by step guidance1
Understand the structure of oxytocin: Oxytocin is a peptide composed of nine amino acids (Cys-Tyr-Ile-Gln-Asn-Cys-Pro-Leu-Gln) arranged in a specific sequence. The peptide chain is held in a cyclic configuration by a disulfide bridge formed between the two cysteine residues.
Recall the structure of a disulfide bridge: A disulfide bridge is a covalent bond formed between the sulfur atoms of two cysteine residues. This bond stabilizes the three-dimensional structure of the peptide.
Draw the linear peptide chain: Begin by sketching the sequence of amino acids in the order provided (Cys-Tyr-Ile-Gln-Asn-Cys-Pro-Leu-Gln). Represent each amino acid with its side chain and backbone structure, ensuring the peptide bonds are correctly shown.
Add the disulfide bridge: Identify the two cysteine residues in the sequence. Connect the sulfur atoms of their side chains with a covalent bond to represent the disulfide bridge, creating the cyclic structure of oxytocin.
Finalize the diagram: Ensure that all atoms are correctly represented, including the hydrogen atoms, oxygen atoms, and nitrogen atoms in the peptide backbone. Label the disulfide bridge and confirm that the cyclic structure is complete and accurate.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Oxytocin Structure
Oxytocin is a nonapeptide hormone composed of nine amino acids, specifically Cys-Tyr-Ile-Gln-Asn-Cys-Pro-Leu-Gln. Its structure is crucial for its biological function, particularly in inducing labor by stimulating uterine contractions. Understanding the sequence and arrangement of these amino acids is essential for visualizing its molecular structure.
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Disulfide Bridge
A disulfide bridge is a covalent bond formed between the sulfur atoms of two cysteine residues in a protein or peptide. In oxytocin, this bridge stabilizes its cyclic configuration, which is important for its activity and interaction with receptors. Recognizing the role of disulfide bridges helps in understanding the stability and functionality of peptide hormones.
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Peptide Diagramming
Diagramming a peptide involves representing its amino acid sequence and structural features, such as disulfide bridges. This visual representation aids in comprehending the spatial arrangement of atoms and the overall conformation of the molecule. Accurate diagramming is essential for illustrating how structural elements contribute to the peptide's biological role.
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