Journal Article

Sequential deletion of C-terminal amino acids of the E<sub>1</sub>α component of the pyruvate dehydrogenase (PDH) complex leads to reduced steady-state levels of functional E<sub>1</sub>α<sub>2</sub>β<sub>2</sub> tetramers: implications for patients with PDH deficiency

Agnieszka Seyda, Gillian McEachern, Richard Haas and Brian H. Robinson

in Human Molecular Genetics

Volume 9, issue 7, pages 1041-1048
Published in print April 2000 | ISSN: 0964-6906
Published online April 2000 | e-ISSN: 1460-2083 | DOI: http://dx.doi.org/10.1093/hmg/9.7.1041
Sequential deletion of C-terminal amino acids of the E1α component of the pyruvate dehydrogenase (PDH) complex leads to reduced steady-state levels of functional E1α2β2 tetramers: implications for patients with PDH deficiency

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Human pyruvate dehydrogenase (PDH) complex deficiency is an extremely heterogeneous disease in its presentation and clinical course. We have characterized novel mutations that affect the C-terminal portion of the PDH-E1α-coding sequence. Although the molecular defects underlying these mutations are different, both effectively produce a stop codon prematurely three amino acids from the C-terminus. The clinical and biochemical consequences of these mutations are unusual in that the affected individuals are very long-term survivors with PDH complex deficiency despite having low (<20%) activity in skin fibroblasts. These findings prompted us to investigate the C-terminus of E1α in greater detail. We constructed and expressed a series of PDH-E1α deletion mutants in a cell line with zero PDH complex activity due to a null E1α allele. Sequential deletion of the C-terminus by one, two, three and four amino acids resulted in PDH complex activities of 100, 60, 36 and 14%, respectively, compared with wild-type E1α expressed in PDH complex-deficient cells. The immunodetectable protein was decreased by the same amount as the activity, suggesting that the stability and/or assembly of the E1α2β2 heterotetramer might depend on the intactness of the PDH-E1α C-terminus. In addition, we compared the somatic and the testis-specific isoforms of E1α and concluded that they are biochemically equivalent.

Journal Article.  6046 words.  Illustrated.

Subjects: Genetics and Genomics

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