Submitted on June 3, 2005
Revised on June 6, 2006
Identification of a 4-mer Peptide Inhibitor that Effectively Blocks the Polymerization of Pathogenic Z 
1-Antitrypsin
Yi-Pin Chang1, Ravi Mahadeva1, Wun-Shaing W. Chang1, Anshuman Shukla1, Tim R Dafforn1, and Yen-Ho Chu1*
1 Department of Chemistry and Biochemistry, National Chung Cheng University, Chai-Yi, Taiwan, Taiwan
* To whom correspondence should be addressed. E-mail: cheyhc{at}ccu.edu.tw.
Alpha-1 antitrypsin (AT) is a major proteinase inhibitor within the lung. The Z variant of AT (E342K) polymerizes within the liver and lung resulting in hepatic aggregation of AT and tissue deficiency, predisposing to early onset of cirrhosis and emphysema, respectively. Polymerization of the aberrant protein can be prevented in vitro by specific peptides such as FLEAIG. This peptide serves as a lead molecule to design a shorter peptide which may be effective as a therapeutic agent. In this study we have used a systematic chemical approach utilizing alanine scanning of Ac-FLEAIG-OH and subsequent peptide shortening to study the binding of shorter peptides to Z-AT. While two additional 6-mer peptides Ac-FLAAIG-OH and Ac-FLEAAG-OH were found to bind to Z-AT, their daughter peptides Ac-FLEAA-NH2 and Ac-FLAA-NH2 also bound avidly to Z-AT and prevented polymerization of the protein. Further comparative studies revealed that the binding of Ac-FLAA-NH2 was more specific for Z-AT. The peptide-AT complex formation was enhanced by the presence of C-terminal amide group on the peptide, and circular dichroism analysis demonstrated that a random coil rather than a 
-helical conformation favored binding of the peptide to AT. In summary, this study has identified novel small peptides which inhibit Z-AT polymerization, and are a significant advance towards the treatment of Z-AT related cirrhosis and emphysema.
