arg-13可能参与鸟氨酸在粗糙脉孢霉线粒体的过膜转运(英文)

arg-13为精氨酸代谢途径里的一个渗露型突变。经研究发展了该突变的严格选择方法。该法省略了基本培养基的氮源而加上相似浓度的鸟氨酸与赖氨酸。此法在严紧山梨糖/葡萄糖条件下能强烈抑制arg-13突变株生长,但在斑点试验条件下允许arg-13突变株生长。由于鸟氨酸是通过线粒体合成和由细胞质至线粒体的过膜转运而积累,我们构建了arg-4,arg-13双突变株,其中arg-4阻断了线粒体鸟氨酸合成。在斑点试验条件下,arg-4,arg-13双突变株能利用鸟氨酸作为唯一氮源与精氨酸合成前体,但受赖氨酸与刀豆氨酸强烈抑制。具正常鸟氨酸转运功能的arg-4单突变株在鸟氨酸基本培养基的生长只受微弱的赖氨酸抑制。已有报道arg-13为嘧啶合成代谢途径里pyr-3(CPSACT~ )突变的部分抑制基因,序列分析表明arg-13编码一线粒体转运酶。本文数据提示arg-13在线粒体鸟氨酸过膜转运过程中起主要作用。arg-13突变株仍携带一定的线粒体鸟氨酸转运功能并受碱性氨基酸赖氨酸、刀豆氨酸抑制,可能为另一线粒体碱性氨基酸转运酶介导。

arg-13 IS IMPLICATED IN MITOCHONDRIAL ORNITHINE TRANSPORT IN NEUROSPORA CRASS A

arg-13 is a leaky mutation involved in argi-nine metabolism. A tight selection is developed using similar amount of lysine and ornithine replacing other nitrogen source in minimal medium. This selection strongly inhibits the growth of arg-13 under stringent sorbose/glucose condition but allows arg-13 to grow under spot test conditions. As ornithine is build up through mi-tochondrial ornithine biosynthesis and transport from cytoplasm to mitochondria, arg-13 is combined in genetic crosses with arg-4 which blocks mitochondrial ornithine synthesis. Under spot test conditions, double mutant arg-4, arg-13 is able to use ornithine as sole nitrogen source and arginine biosynthesis precursor, but subject to strong lysine and canavanine inhibition. While the usage of ornithine in arg-4 single mutant with intact ornithine transport function is only slightly inhibited by lysine. All available data suggest arg-13 plays a major role in mitochondrial ornithine transport. The strain carrying the mutation at the arg-13 locus allows inefficient mitochondrial ornithine trafficking, possibly mediated by another distinct basic amino acid carrier.