Structural Change in β-Sheet A of Z α1-Antitrypsin Is Responsible for Accelerated Polymerization and Disease

Knaupp, Anja S; Bottomley, Stephen P.

doi:10.1016/j.jmb.2011.09.013

Cited by 17 publications

(35 citation statements)

References 48 publications

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“…The environment-sensitive dye bis-ANS reports the presence of a hydrophobic binding site, which coincides with the transition to a polymerization intermediate (31). This dye displays enhanced fluorescence in the presence of the AT Z mutant (30) and yielded a comparable increase in AT A336P fluorescence over that of AT M ( Figure 2C), consistent with an increased population of the intermediate state.…”

Section: Ala336pro Mutation Reduces the Inhibitory Activity Of Alpha-mentioning

confidence: 82%

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Deficiency Mutations of Alpha-1 Antitrypsin. Effects on Folding, Function, and Polymerization

Haq

Irving

Saleh

et al. 2016

Am J Respir Cell Mol Biol

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Misfolding, polymerization, and defective secretion of functional alpha-1 antitrypsin underlies the predisposition to severe liver and lung disease in alpha-1 antitrypsin deficiency. We have identified a novel (Ala336Pro, Baghdad) deficiency variant and characterized it relative to the wild-type (M) and Glu342Lys (Z) alleles. The index case is a homozygous individual of consanguineous parentage, with levels of circulating alpha-1 antitrypsin in the moderate deficiency range, but is a biochemical phenotype that could not be classified by standard methods. The majority of the protein was present as functionally inactive polymer, and the remaining monomer was 37% active relative to the wild-type protein. These factors combined indicate an 85 to 95% functional deficiency, similar to that seen with ZZ homozygotes. Biochemical, biophysical, and computational studies further defined the molecular basis of this deficiency. These studies demonstrated that native Ala336Pro alpha-1 antitrypsin could populate the polymerogenic intermediate-and therefore polymerize-more readily than either wild-type alpha-1 antitrypsin or the Z variant. In contrast, folding was far less impaired in Ala336Pro alpha-1 antitrypsin than in the Z variant. The data are consistent with a disparate contribution by the "breach" region and "shutter" region of strand 5A to folding and polymerization mechanisms. Moreover, the findings demonstrate that, in these variants, folding efficiency does not correlate directly with the tendency to polymerize in vitro or in vivo. They therefore differentiate generalized misfolding from polymerization tendencies in missense variants of alpha-1 antitrypsin. Clinically, they further support the need to quantify loss-of-function in alpha-1 antitrypsin deficiency to individualize patient care.

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Section: Ala336pro Mutation Reduces the Inhibitory Activity Of Alpha-mentioning

confidence: 82%

“…The center of spectral mass (COSM), calculated from intrinsic fluorescence of (30). Intrinsic protein fluorescence spectra were collected during pseudo-equilibrium unfolding of the three variants, and COSM values were calculated.…”

Section: Ala336pro Mutation Reduces the Inhibitory Activity Of Alpha-mentioning

confidence: 99%

Deficiency Mutations of Alpha-1 Antitrypsin. Effects on Folding, Function, and Polymerization

Haq

Irving

Saleh

et al. 2016

Am J Respir Cell Mol Biol

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“…For a combined analysis, five published datasets are considered in the present study [28,29,49–51]; when combined with the 60°C data described in the present paper, this represents 36 unique mutants. These datasets differ in the manner in which T m value was determined (CD and SYPRO Orange), the T m value reported for the wild-type control, the temperature at which polymerization was recorded (45°C, 52°C and 60°C) and the means by which it was monitored (tryptophan fluorescence and non-denaturing PAGE analysis).…”

Section: Resultsmentioning

confidence: 99%

“…Polymerization rates were obtained from studies reported in the literature in which values had been determined from the loss of monomer as observed by native gel densitometry [29,49–51] and using intrinsic tryptophan fluorescence [28]. In the case of gel images presented by Gilis et al [29], densitometry was performed retrospectively using GelAnalyzer 2010a software (http:://gelanalyzer.com).…”

Section: Methodsmentioning

confidence: 99%

Altered native stability is the dominant basis for susceptibility of α1-antitrypsin mutants to polymerization

Irving

Haq

Dickens

et al. 2014

Biochemical Journal

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Serpins are protease inhibitors whose most stable state is achieved upon transition of a central 5-stranded β-sheet to a 6-stranded form. Mutations, low pH, denaturants and elevated temperatures promote this transition, which can result in a growing polymer chain of inactive molecules. Different types of polymer are possible, but, experimentally only heat has been shown to generate polymers in vitro consistent with ex vivo pathological specimens. Many mutations that alter the rate of heat-induced polymerization have been described, but interpretation is problematic because discrimination is lacking between the effect of global changes in native stability and specific effects on structural mechanism. We show that the temperature midpoint (Tm) of thermal denaturation reflects the transition of α1-antitrypsin to the polymerization intermediate, and determine the relationship with fixed-temperature polymerization half-times (t0.5) in the presence of stabilizing additives [TMAO (trimethylamine N-oxide), sucrose and sodium sulfate], point mutations and disulfide bonds. Combined with a retrospective analysis of 31 mutants characterized in the literature, the results of the present study show that global changes to native state stability are the predominant basis for the effects of mutations and osmolytes on heat-induced polymerization, summarized by the equation: ln(t0.5,mutant/t0.5,wild-type)=0.34×ΔTm. It is deviations from this relationship that hold key information about the polymerization process.

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“…9). In addition, a recent study using single tryptophan variants of ␣ 1 PI demonstrated a structural difference between wild-type and Z variant ␣ 1 PIs in the vicinity of the mutation at the top of the A sheet, suggestive of greater solvent accessibility in this region (23), perhaps resulting from a widened opening at the top of the sheet.…”

Section: Folding Of Z Variant Slowedmentioning

confidence: 98%

How the Serpin α1-Proteinase Inhibitor Folds

Dolmer

Gettins

2012

Journal of Biological Chemistry

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Background: Functional serpins uniquely adopt a metastable conformation by an unknown folding pathway. Results: Ability of constituent ␣ 1 -proteinase inhibitor (␣ 1 PI) peptides to associate reveals the order of folding. Conclusion: Metastability results from the inability of sheet A strand 4 to efficiently insert before completion of C-terminal sheet B. Significance: Pathway helps explains the nature of the polymerogenic intermediate of the Z variant of ␣ 1 PI.

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Structural Change in β-Sheet A of Z α1-Antitrypsin Is Responsible for Accelerated Polymerization and Disease

Cited by 17 publications

References 48 publications

Deficiency Mutations of Alpha-1 Antitrypsin. Effects on Folding, Function, and Polymerization

Deficiency Mutations of Alpha-1 Antitrypsin. Effects on Folding, Function, and Polymerization

Altered native stability is the dominant basis for susceptibility of α1-antitrypsin mutants to polymerization

How the Serpin α1-Proteinase Inhibitor Folds

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