Question

An antibody is very specific for an epitope, such as a region of a protein. A researcher performs a Western blot using an antibody that is specific to her unique protein of interest and sees three distinct band sizes on her blot - one at the expected size, one slightly larger than the expected size, and the other slightly smaller than the expected size. She confirms that for her samples, the gene encoding this protein is in the homozygous wild-type state. She reproduces the result with multiple blots and independent samples, so she knows the size differences are not due to an experimental artifact.

Briefly describe at least two biological mechanisms that may explain how she could have detected three different sizes of the same protein.

Answer 1

The results has been seen because of slightly change in molecular weight it can be by the post-translational modification in particular Amino acids like glycosylation or something else.

As antibody binds to a particular epitope if some protein has been changed in regions other than epitope, it will not affect the binding that why the band can be seen in slightly lower position.

It can also be splicing modification in which one protein is produced and other is produced which has partly same Ami o acid sequence and some different segments. So, here both will bind antibody and will give band.

It can also be digestion or cleavage of protein after synthesis , which can also be lower than molecular weight of protein but will not affect the binding with antibody.

Thank you