Stadler Sonja C, Polanetz Roman, Meier Stephan, Mayerhofer Peter U, Herrmann Johannes M, Anslinger Katja, Roscher Adelbert A, Röschinger Wulf, Holzinger Andreas
Dr. von Hauner Children's Hospital, Department of Biochemical Genetics and Molecular Biology, Ludwig-Maximilians-University, Munich, Germany.
Biochem Biophys Res Commun. 2005 Sep 2;334(3):939-46. doi: 10.1016/j.bbrc.2005.06.190.
Inherited deficiency of 3-methylcrotonyl-CoA carboxylase (MCC), an enzyme of leucine degradation, is an organic acidemia detectable by expanded newborn screening with a variable phenotype that ranges from asymptomatic to death in infancy. Here, we show that the two subunits of the enzyme (MCCalpha; MCCbeta) are imported into the mitochondrial matrix by the classical pathway involving cleavable amino-terminal targeting presequences. We identified the cleavage sites (Tyr41/Thr42 and Ala22/Tyr23 for MCCalpha and MCCbeta, respectively) of the targeting signals and the amino-termini of the mature polypeptides of MCC and propionyl-CoA carboxylase, a mitochondrial paralog. The amino-termini containing 39 (MCCalpha) or 20 amino acids (MCCbeta) were both necessary and sufficient for targeting. Structural requirements for mitochondrial import were defined by site-directed mutagenesis. Our studies provide the prerequisite to understand the impact of specific mutations on the clinical phenotype of MCC deficiency.
3-甲基巴豆酰辅酶A羧化酶（MCC）是亮氨酸降解过程中的一种酶，其遗传性缺乏是一种有机酸血症，可通过扩大新生儿筛查检测出来，其表型各异，从无症状到婴儿期死亡不等。在此，我们表明该酶的两个亚基（MCCα；MCCβ）通过涉及可裂解氨基末端靶向前序列的经典途径导入线粒体基质。我们确定了靶向信号的切割位点（MCCα和MCCβ分别为Tyr41/Thr42和Ala22/Tyr23）以及MCC和线粒体旁系同源物丙酰辅酶A羧化酶成熟多肽的氨基末端。含有39个氨基酸（MCCα）或20个氨基酸（MCCβ）的氨基末端对于靶向而言既是必需的也是足够的。通过定点诱变确定了线粒体导入的结构要求。我们的研究为理解特定突变对MCC缺乏临床表型的影响提供了前提条件。
