Tertiary Structure and Sickle Cell Anemia

Tertiary structure involves interactions of R groups within the protein chain.
Amino acids can be distant from each other in the protein chain, but when the protein folds, their R groups come into close proximity.
This differs from secondary structure, where carbonyl and amine groups need to be close together.

Sickle cell anemia is a genetic disease used as an example to explain how protein denaturation can affect cells.
The mutation in sickle cell anemia occurs in the beta globin gene.
In this gene, the amino acid glutamate is replaced by valine.
Even a change of one amino acid creates complications within cells, even when the alpha chains are normal.

Hemoglobin's primary function is to carry oxygen.
Red blood cells are essentially sacs of hemoglobin, making up about 90% of their content.
Heme groups are located in the middle of each globin polypeptide within the hemoglobin.
Each heme group contains iron, which binds to oxygen.
Ideally, each hemoglobin molecule should bind to four oxygen molecules.

When oxygen is bound to hemoglobin in individuals with sickle cell anemia, the cells appear normal.
However, when oxygen is not bound, the shape of the hemoglobin protein changes.
If a sufficient number of hemoglobin molecules within a cell change shape, the entire cell's shape is altered to the characteristic sickle shape.
This shape change leads to the problems associated with sickle cell anemia.
The visual change demonstrates how mutations and changes in shape can have significant effects at the cellular level.

The specific amino acid change (glutamate to valine) will not be specifically tested.
This example serves to illustrate the visual impact of protein mutations and their effects.