Mechanisms for Intragenic Complementation at the Human Argininosuccinate Lyase Locus

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• 作者：Bomina Yu ; Gawen D. Thompson ; Patrick Yip ; P. Lynne Howell ; and Alan R. Davidson
• 刊名：Biochemistry
• 出版年：2001
• 出版时间：December 25, 2001
• 年：2001
• 卷：40
• 期：51
• 页码：15581 - 15590
• 全文大小：368K
• 年卷期：v.40,no.51(December 25, 2001)
• ISSN：1520-4995

文摘

Argininosuccinate lyase (ASL) is a homotetrameric enzyme that catalyzes the reversible cleavageof argininosuccinate to arginine and fumarate. Deficiencies in the enzyme result in the autosomal, recessivedisorder argininosuccinic aciduria. Considerable clinical and genetic heterogeneity is associated withthis disorder, which is thought to be a consequence of the extensive intragenic complementation identifiedin patient strains. Our ability to predict genotype-phenotype relationships is hampered by the currentlack of understanding of the mechanisms by which complementation can occur. The 3-dimensional structureof wild-type ASL has enabled us to propose that the complementation between two ASL active site mutantsubunits, Q286R and D87G, occurs through a regeneration of functional active sites in the heteromutantprotein. We have reconstructed this complementation event, both in vivo and in vitro, using recombinantproteins and have confirmed this hypothesis. The complementation events between Q286R and twononactive site mutants, M360T and A398D, have also been characterized. The M360T and A398Dsubstitutions have adverse effects on the thermodynamic stability of the protein. Complementation betweeneither the M360T or the A398D mutant and the stable Q286R mutant occurs through the formation of amore stable heteromeric protein with partial recovery of catalytic activity. The detection and characterizationof a novel complementation event between the A398D and D87G mutants has shown how complementationin patients with argininosuccinic aciduria may correlate with the clinical phenotype.