The vital interplay of acyl-carrier proteins and LYR proteins (ACPM-LYRM) in mitochondria

线粒体宿主的基本生化途径，如氧化磷酸化（OXPHOS）系统，Fe-S簇生物合成和氧化。此外，线粒体含有以细菌II型模式（FAS II）合成脂肪酸的所有酶。高度保守的线粒体FAS II机制的中心元件是线粒体酰基载体蛋白（ACPM）。真核LYR（亮氨酸/酪氨酸/精氨酸）基序蛋白（LYRMs）属于Complex 1-LYR-like超家族，是线粒体OXPHOS复合物I、II、III和V的新亚基或组装因子，被认为是ACPM的相互作用伙伴。在来自需氧酵母解脂耶氏酵母的复合物I中，ACPM 1和LYRM 6以及ACPM 2和LYRM 3分别形成两个明确定义的辅助结构域，这两个辅助结构域对于酶活性或组装是必需的。然而，在3.6-3.9埃分辨率的X射线结构中，Y.解脂酶复合体I和在最近对牛复合体I的远端膜臂模块的中分辨率X射线结构分析中，所有四种蛋白质仅被模拟为聚丙氨酸。我的初步工作强烈表明，ACPM 1的一部分共存与LYRM 4（ISD 11）-NFS 1复合物参与Fe-S簇生物发生和作为一个自由的基质蛋白（matrix-ACPM 1），分别。ACPM 1-LYRM 4/NFS 1复合物的分离与本文提出的新型多组分硫辛酸合成复合物一致。与复合物I亚基ACPM（CI-ACPM）相反，基质-ACPM 1是N-末端乙酰化的，表明将ACPM 1分配至基质或复合物I的亚线粒体分选机制。最初的质谱数据表明，一部分基质-ACPM 1携带新生脂肪酸链（C9-C16-酰基-ACPM 1中间体）。我们检测到更高质量的酰基连接到CI-ACPM 1和CI-ACPM 2，但他们的身份仍然不清楚。该项目的一个主要重点将是解开基质-ACPM 1的功能，并解决ACPM 1-LYRM 4/NFS 1复合物在硫辛酸合成中的作用。我的目标是一方面了解ACPM 1与线粒体复合物I的关联，另一方面了解ACPM 1与NFS 1复合物的关联，这一目标的重要一步将是确定结合的酰基。ACPM 1、LYRM 6和ACPM 1-LYRM 4/NFS 1复合物的结构测定将揭示ACPM 1锚定到LYRM的分子基础，并有望提供为什么ACPM-LYRM结构域的存在对于复合物I和NFS 1蛋白的功能至关重要的重要线索。

Mitochondria host essential biochemical pathways such as the oxidative phosphorylation (OXPHOS) system, Fe-S cluster biogenesis and -oxidation. Furthermore, mitochondria contain all enzymes to synthesize fatty acids in the bacterial type II mode (FAS II). A central element of the highly conserved mitochondrial FAS II machinery is the mitochondrial acyl-carrier protein (ACPM). Eukaryotic LYR (leucine/tyrosine/arginine) motif proteins (LYRMs) of the Complex1-LYR-like superfamily, that are mostly novel subunits or assembly factors of mitochondrial OXPHOS complexes I, II, III and V, were suggested as interaction partners for ACPM. In complex I from the aerobic yeast Yarrowia lipolytica ACPM1 and LYRM6, and ACPM2 and LYRM3, form two well defined accessory domains that are essential for enzymatic activity or assembly, respectively. However, in the 3.6-3.9 A resolution X-ray structure of Y. lipolytica complex I and in a recent intermediate resolution X-ray structural analysis of the distal membrane arm module of Bos taurus complex I all four proteins were only modeled as poly-alanine. My preliminary work strongly suggests that a fraction of ACPM1 coexists associated with the LYRM4(ISD11)-NFS1 complex involved in Fe-S cluster biogenesis and as a free matrix protein (matrix-ACPM1), respectively. The isolation of the ACPM1-LYRM4/NFS1 complex is consistent with a here proposed novel multi-component lipoic acid synthesis complex. In contrast to complex I subunit ACPMs (CI-ACPM), matrix-ACPM1 is N-terminally acetylated suggesting an sub-mitochondrial sorting mechanism that distributes ACPM1 to the matrix or to complex I. Initial mass spectrometry data indicated that a fraction of matrix-ACPM1 carries a nascent fatty acid chain (C9-C16-acyl-ACPM1 intermediates). We detected higher mass acyl groups attached to CI-ACPM1 and CI-ACPM2 but their identities are still unclear. A major focus of this project will be to unravel the function of matrix-ACPM1 and to resolve the role of the ACPM1-LYRM4/NFS1 complex in lipoic acid synthesis. An important step towards my goal to understand the association of ACPM1 with mitochondrial complex I on one hand and with the NFS1 complex on the other hand will be to identify the bound acyl groups. Structure determination of ACPM1, LYRM6 and of the ACPM1-LYRM4/NFS1 complex will reveal the molecular basis for anchoring of ACPM1 to LYRMs and is expected to provide important clues why the presence of an ACPM-LYRM domain is critical for the function of complex I and the NFS1 protein.