Can the same amino acid sequences could fold differently?

Different protein sequences can give rise to highly similar folds through different stabilizing interactions. Beckman Laboratories for Structural Biology, Department of Cell Biology, Stanford University School of Medicine, California 94305.

Do all proteins fold into the same shape?

Each protein normally folds up into a single stable conformation. However, the conformation often changes slightly when the protein interacts with other molecules in the cell. Proteins come in a wide variety of shapes, and they are generally between 50 and 2000 amino acids long.

Why are two proteins with the same amino acid composition do not have the same primary structure?

No two proteins with different amino acid sequences (primary structure) have identical overall structure. The unique amino acid sequence of a protein is reflected in its unique folded structure. This structure, in turn, determines the protein’s function.

How can two proteins with exactly the same number and type of amino acids have different primary structures?

The order of the amino acids (primary structure) in the two proteins may be different. This can result in ionic, hydrogen and disulphide bonds to form in different locations in each protein. Such differences may cause variations in the three dimensional structures of the proteins (tertiary structure).

Can a protein fold properly even if a few of its amino acids do not satisfy the basic rules?

In general, it depends on the substitution between the desired amino acid and the one being substituted. If the side-chains are similar enough, then the bonding mechanisms that cause the fold could still occur appropriately.

Why do proteins have different shapes if they are all composed of amino acids?

Each protein has its own unique sequence of amino acids and the interactions between these amino acids create a specify shape. This shape determines the protein’s function, from digesting protein in the stomach to carrying oxygen in the blood.

Why do different proteins contain a different number and a different sequence of amino acids?

Proteins different in length and compositions because the sequence that makes them (their gene) is composed of different nucleotides. Different genes have different nucleotide sequences, and hence different proteins are produced.