Question

Functional assays vs. protein density: what happens to each if protein is denatured

Answer 1

Protein biochemistry requires use of both, structural as well as functional quantitation of proteins. In this regard, two major types of systems have been generated to investigate proteins, functional assays which tend to investigate the functional aspects of proteins such as enzyme activity and the quantitative assays which tend to investigate the total amount of protein in a given sample such as protein density, abundance etc.

Here, it is important to note that biological activity of a protein is a function of its structure. This is because a protein represents to be a highly conserved structure in quarternary orientation which perfomrs a biological function. If any structural deterioration takes place in this structure, the protein function will be interrupted or altogether halted. Hence, denatured proteins show decline or negative functional assays.

On the other hand, structural disorientation due to denaturation does not promote decrease in total protein content in a sample. This is because even after denaturation, the total content of the protein remains same and hence the quantity is not altered. Thus, a protein density or quantitative assay remains un-interrupted.

For example, the functional assay of a denatured enzyme would be negative in nature whereas the protein density of the enzyme would remain same.