The linear sequence of amino acids is referred to as the primary level of protei
ID: 47578 • Letter: T
Question
The linear sequence of amino acids is referred to as the primary level of protein structure. However, the primary sequence affects all other aspects of protein structure. 1) Explain how an amino acid change outside of the active site of a particular enzyme could affect the function of that enzyme. 2) Explain how that same amino acid change could have no affect on the function of the enzyme. 3) Imagine a protein in which a cysteine is converted to a serine. How would this mutation affect the secondary, tertiary and quaternary structure?Explanation / Answer
Answer
1) The linear sequence of the amino acids constitutes the primary structure of the protein and all the properties of a protein are derived from the primary structure. Almost all the biological functions are expressed when two molecules bind to each other. A protein must bind to its specific substrate to provoke a response, however if, the amino acid change outside the active site would alter the shape of the enzyme protein and the active site will no longer be able to bind to its appropriate substrate . Since active site is substrate specific any changes in it, will result in no binding of the substrate and the rate of reaction would decrease.
2) If the same amino acid changes, still the shape of the enzyme protein will not change and hence, the shape of the active site remains same. Then, the substrate would bind to its active site and carry out the reaction. Therefore, the function of the enzyme is not affected.
3) The sequence of a protein is determined by the genes encoding the protein. A change in the gene's DNA will change the amino acid sequence of protein. Mutation caused by change of single amino acid can affect the overall structure of the protein. For instance, cysteine is a thiol group containing amino acid responsible for disulfide bonds that hold the tertiary structure together. If the cysteine is mutated to serine, this can code to a different protein leading to incorrect folding.
The change in single amino acid of the protein is directly related to disease. For instance, in a secondary structure a change in single amino acid at position 6 in the beta chain of hemoglobin can result in aggregation of the hemoglobin molecules and also affects the fragility of the red blood cells. A protein to be functional, it must have an intact tertiary structure, change in the amino acid sequence caused by gene mutation can lead to destruction of the protein structure making it unable to perform its intended function. The quaternary structure is the total protein made when all the subunits of the protein are in their intact place. Mutations in any of the above structures would alter the quaternary structure and its ability to function.
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.