Cavities of α1-antitrypsin that play structural and functional roles |
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Authors: | Cheolju Lee Jin-Soo Maeng Jean-Pierre Kocher Byungkook Lee Myeong-Hee Yu |
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Affiliation: | National Creative Research Initiatives, Protein Strain Research Center, Korea Institute of Science and Technology, Cheongryang, Seoul 130-650, Korea. |
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Abstract: | The native form of inhibitory serine protease inhibitors (serpins) is strained, which is critical for their inhibitory activity. Previous studies on stabilizing mutations of alpha(1)-antitrypsin, a prototype of serpins, indicated that cavities provide a structural basis for the native strain of the molecule. We have systematically mapped the cavities of alpha(1)-antitrypsin that play such structural and functional roles by designing cavity-filling mutations at residues that line the walls of the cavities. Results show that energetically unfavorable cavities are distributed throughout the alpha(1)-antitrypsin molecule, and the cavity-filling mutations stabilized the native conformation at 8 out of 10 target sites. The stabilization effect of the individual cavity-filling mutations of alpha(1)-antitrypsin varied (0.2-1.9 kcal/mol for each additional methylene group) and appeared to depend largely on the structural flexibility of the cavity environment. Cavity-filling mutations that decreased inhibitory activity of alpha(1)-antitrypsin were localized in the loop regions that interact with beta-sheet A distal from the reactive center loop. The results are consistent with the notion that beta-sheet A and the structure around it mobilize when alpha(1)-antitrypsin forms a complex with a target protease. |
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Keywords: | α1-antitrypsin cavity-filling mutations conformational stability native strain molecular packing |
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