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  • Title: The Z mutation alters the global structural dynamics of α1-antitrypsin.
    Author: Hughes VA, Meklemburg R, Bottomley SP, Wintrode PL.
    Journal: PLoS One; 2014; 9(9):e102617. PubMed ID: 25181470.
    Abstract:
    α1-Antitrypsin (α1AT) deficiency, the most common serpinopathy, results in both emphysema and liver disease. Over 90% of all clinical cases of α1AT deficiency are caused by the Z variant in which Glu342, located at the top of s5A, is replaced by a Lys which results in polymerization both in vivo and in vitro. The Glu342Lys mutation removes a salt bridge and a hydrogen bond but does not effect the thermodynamic stability of Z α1AT compared to the wild type protein, M α1AT, and so it is unclear why Z α1AT has an increased polymerization propensity. We speculated that the loss of these interactions would make the native state of Z α1AT more dynamic than M α1AT and that this change renders the protein more polymerization prone. We have used hydrogen/deuterium exchange combined with mass spectrometry (HXMS) to determine the structural and dynamic differences between native Z and M α1AT to reveal the molecular basis of Z α1AT polymerization. Our HXMS data shows that the Z mutation significantly perturbs the region around the site of mutation. Strikingly the Z mutation also alters the dynamics of regions distant to the mutation such as the B, D and I helices and specific regions of each β-sheet. These changes in global dynamics may lead to an increase in the likelihood of Z α1AT sampling a polymerogenic structure thereby causing disease.
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