Altered specificities of genetically engineered alpha 1 antitrypsin variants

Area of Science:

• Biochemistry
• Molecular Biology
• Enzyme Inhibition

Background:

• Human alpha 1-antitrypsin (alpha 1AT) is a key serine protease inhibitor.
• Understanding alpha 1AT's structure-activity relationship is crucial for therapeutic development.

Purpose of the Study:

• To engineer and characterize novel human alpha 1AT variants with altered protease inhibition profiles.
• To investigate the impact of specific amino acid substitutions at the P1 and P3 positions on inhibitor activity.

Main Methods:

• Site-specific mutagenesis of alpha 1AT complementary DNA to create active site variants.
• Production of mutant alpha 1AT proteins in Escherichia coli.
• Assays to evaluate the inhibitory activity of variants against neutrophil elastase, pancreatic elastase, cathepsin G, and thrombin.
• SDS-PAGE to analyze protease-inhibitor complex formation.

Main Results:

• Seven active site variants of alpha 1AT were successfully produced.
• Variants alpha 1AT (Ala358), alpha 1AT (Ile358), and alpha 1AT (Val358) inhibited neutrophil and pancreatic elastases.
• alpha 1AT (Leu358) demonstrated potent inhibition of neutrophil elastase and cathepsin G.
• alpha 1AT (Arg358) inactivated thrombin, mimicking antithrombin III activity.
• SDS-stable complexes confirmed protease inhibition by mutant alpha 1AT proteins.

Conclusions:

• Effective protease inhibition by alpha 1AT requires correspondence between its P1 residue and the target protease's specificity.
• Modifications at the P3 residue can further modulate inhibitor reactivity.
• alpha 1AT (Leu358) and alpha 1AT (Arg358) variants exhibit therapeutic potential for lung disorders and thrombosis, respectively.