Identification and characterization of human haptoglobin cDNA

Area of Science:

• Molecular Biology
• Biochemistry
• Genetics

Background:

• Haptoglobin (Hp) is a plasma protein crucial for binding free hemoglobin.
• Understanding Hp's structure is vital for comprehending its function and evolution.

Purpose of the Study:

• To isolate and characterize human haptoglobin cDNA.
• To elucidate the structural basis of mature haptoglobin formation.
• To investigate the evolutionary relationship between haptoglobin and serine proteases.

Main Methods:

• Screening an adult human liver cDNA library using a mixed oligonucleotide probe.
• Isolation and sequencing of four cDNA clones containing haptoglobin inserts (1,218 nucleotides).
• Sequence analysis to identify coding regions, leader sequence, and chain structures.

Main Results:

• Successfully isolated human haptoglobin cDNA clones.
• Identified a leader sequence, alpha 2-chain, and beta-chain sequences.
• Deduced a previously unknown arginine residue between alpha- and beta-chain sequences, a probable proteolysis site.
• Established the alignment of the Hp alpha 2 gene sequence.

Conclusions:

• The identified cDNA sequence provides a comprehensive understanding of haptoglobin's genetic makeup.
• The novel arginine residue offers insight into the post-translational processing of haptoglobin.
• The study reinforces the evolutionary homology between haptoglobin and serine proteases.