Question

Explain the technique of peptide mapping used to compare normal haemoglobin with sickle cell haemoglobin.

Hint:

Peptide mapping identifies differences in protein structure by comparing enzyme-generated peptide fragments, useful for detecting mutations like in sickle cell haemoglobin.

Answer 1

Peptide Mapping is a method for protein analysis and comparison. It involves fragmenting proteins into peptides and examining their patterns to identify structural variations, often due to mutations.

• Both normal haemoglobin and sickle cell haemoglobin undergo enzymatic digestion using enzymes like trypsin, which cut proteins at specific amino acid sequences.
• This enzymatic action yields smaller peptide fragments unique to each protein's sequence.
• These peptide fragments are then separated using techniques such as chromatography or electrophoresis, categorized by their size and charge.
• The distinct pattern of these peptide fragments (the peptide map) is then visualized, typically through staining or autoradiography.
• In sickle cell haemoglobin, a single amino acid alteration (glutamic acid replaced by valine) modifies the peptide fragments, resulting in a distinct pattern compared to normal haemoglobin.
• This observable difference in the peptide map serves as confirmation of the molecular cause of sickle cell anaemia.