Import rate of the E1β subunit of human branched chain α-ketoacid dehydrogenase is a limiting factor in the amount of complex formed in the mitochondria
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- 作者：Sitler ; Tracy L. ; McKean ; Martha C. ; Peinemann ; Frank ; Jackson ; Elizabeth ; Danner ; Dean J.
- 关键词：Protein import ; Mitochondrion ; Branched chain α ; -ketoacid dehydrogenase
- 刊名：Biochimica et Biophysica Acta (BBA)/Molecular Cell Research
- 出版年：1998
- 出版时间：September 16, 1998
- 年：1998
- 卷：1404
- 期：3
- 页码：385-392
- 全文大小：308 K
文摘
Components of the mitochondrial branched chain α-ketoacid dehydrogenase multienzyme complex are all encoded by nuclear genes. The functional complex is formed with a known stoichiometric relationship of subunits, but how they enter the mitochondria and form the complex is not defined. Although cytosolic precursors for several of the proteins have been identified, the requirements for import and processing have not been described. Here we demonstrate the similar requirements for in vitro import and processing of the three catalytic subunits unique the this complex. Import was not affected by the amount of endogenous BCKD within the mitochondria. No cooperativity or competition among the subunits for import was found when subunits were used in combination. The relative rates of entry are E1α>E2≥E1β, making E1β the limiting component supporting previously reported observations.