831 MOLECULAR HETEROGENEITY OF ELECTRON TRANSFER FLAVOPROTEIN (ETF) IN GLUTARIC ACIDURIA TYPE II DUE TO AN ETF DEFICIENCY

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Glutaric aciduria type II (GAII) is due to a deficiency of either ETF or ETF dehydrogenase. We studied the biosynthesis of ETF in 10 GAII lines as well as in normal controls. Cells were labeled with [35S]methionine in the presence and absence of rhodamine 6G. Rhodamine 6G inhibits mitochondrial ATP synthesis, thereby inhibiting post-translational processing of the nuclear coded mitochondrial enzymes. The labeled human ETF was immunoprecipitated from the solubilized cells using the anti-rat ETF antiserum and Staph A cells and analyzed by SDS-PAGE. In normal cells, α-subunit is synthesized as a precursor (35 kd), 3 kd larger than the mature counterpart (32 kd), while β-subunit is synthesized in a size indistinguishable from that of the mature β-subunit (27 kd). ETF abnormality was found in three GAII lines. In two of them, α-subunit was synthesized either not at all or in an extremely small amount. The size of the precursor and mature forms of ETF were of the normal sizes. In contrast, α-subunit synthesized in the third GAII line was 1 kd smaller than the normal size, both as precursor and mature form. In all other 7 GAII lines, the synthesis of α-subunit were normal. These 7 cell lines are due to an ETF dehydrogenase deficiency. Abnormality of β-subunit was found in none of the cell lines tested.