Kinetic instability of the serpin Z alpha1-antitrypsin promotes aggregation

The serpinopathies encompass a large number of diseases caused by inappropriate conformational change and self-association (polymerization) of a serpin (serine proteinase inhibitor) molecule. The most common serpinopathy is alpha(1)-antitrypsin (alpha(1)AT) deficiency, which is associated with an in...

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Bibliographic Details
Published in:Journal of molecular biology 2010-02, Vol.396 (2), p.375-383
Main Authors: Knaupp, Anja S, Levina, Vita, Robertson, Amy L, Pearce, Mary C, Bottomley, Stephen P
Format: Article
Language:English
Subjects:
alpha 1-Antitrypsin - chemistry
alpha 1-Antitrypsin - metabolism
Chemical Precipitation
Humans
Kinetics
Models, Molecular
Protein Conformation
Protein Folding
Protein Isoforms - chemistry
Protein Isoforms - metabolism
Protein Stability
Serpins - chemistry
Serpins - metabolism
Thermodynamics
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Summary:The serpinopathies encompass a large number of diseases caused by inappropriate conformational change and self-association (polymerization) of a serpin (serine proteinase inhibitor) molecule. The most common serpinopathy is alpha(1)-antitrypsin (alpha(1)AT) deficiency, which is associated with an increased risk for liver cirrhosis, hepatocellular carcinoma and early-onset emphysema. The Z variant of alpha(1)AT, which accounts for 95% of all cases of alpha(1)AT deficiency, polymerizes during synthesis and after secretion. Here, we show using intrinsic and extrinsic fluorescence probes that Z alpha(1)AT exists in a non-native conformation. We examined the thermodynamic stability by transverse urea gradient gel electrophoresis, thermal denaturation and equilibrium guanidine hydrochloride unfolding and found that, despite structural differences between the two proteins, wild-type alpha(1)AT and Z alpha(1)AT display similar unfolding pathways and thermodynamic stabilities. Far-UV circular dichroism and bis-ANS (4,4'-dianilino-1,1'-binaphthyl-5,5'-disulfonic acid, dipotassium salt) fluorescence suggest that the intermediate ensembles formed during unfolding of wild-type alpha(1)AT and Z alpha(1)AT are characterized by similar structural features. Kinetic analysis of the unfolding transition showed that Z alpha(1)AT unfolds at least 1.5-fold faster than the wild type. The biological implications of these data are discussed.
ISSN:1089-8638
DOI:10.1016/j.jmb.2009.11.048