Part D - Where does a protein begin and end?

Question

The position of every amino acid in a protein is determined by the folding pattern of the polypeptide chain. Some amino acids are internal and help to hold the protein’s shape. Others are external and provide an opportunity to interact with other molecules. In addition, the position of certain amino acids is absolutely essential for the function of the protein.

Launch the molecular model to explore the folding pattern of the lysozyme protein. Make sure to use the interactive structure window to display amino acids A, B, and C.
Select to launch molecular model

After exploring the molecular model, answer this question.

In the 3D, or tertiary, structure of the protein shown in the interactive structure window, the amino acid labeled C appears to be positioned between the amino acids labeled A and B.
Which amino acid--A, B, or C--actually falls between the other two in lysozyme’s primary structure (the order of the amino acids in the polypeptide chain)?

A
B
C

Answer 1

To determine which amino acid—A, B, or C—actually falls between the other two in lysozyme’s primary structure, we need to recall how the primary structure of a protein is defined. The primary structure refers to the linear sequence of amino acids in the polypeptide chain, which is determined by the gene encoding the protein.

In the context provided, if amino acid C is positioned in the 3D structure between A and B, it does not necessarily mean it is located between them in the primary structure. To correctly answer the question, we typically would need to know the specific sequence of lysozyme's primary structure.

However, in many cases, when analyzing protein structures, it’s common for the 3D conformation to differ from the linear sequence due to folding. While the arrangement in tertiary structure can give clues, only the primary sequence can definitively tell the order of the amino acids.

Since I don’t have the specific sequence of lysozyme in this context, the best action would be to refer to a known sequence database of lysozyme and observe which amino acid is positioned linearly between the others.

In conclusion, without that specific data or context of the sequence, it would not be possible to definitively state which amino acid A, B, or C lies between the others in the primary structure. It is commonly expected that the linear order in the primary structure would be assessed for an accurate answer.