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

线粒体具有重要的生化途径，如氧化磷酸化（OXPHOS）系统，Fe-S簇生物发生和氧化。此外，线粒体含有细菌II型模式（FAS II）中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）。Complex1-LYR-like超家族的真核LYR（亮氨酸/酪氨酸/精氨酸）基序蛋白（lyrm），主要是线粒体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。在需氧酵母解脂耶氏菌的复合体I中，ACPM1和LYRM6以及ACPM2和LYRM3形成了两个明确的辅助结构域，分别是酶活性或组装所必需的。然而，在脂肪瘤Y. polytica复合体I的3.6-3.9 A分辨率x射线结构和最近对Bos taurus复合体I远端膜臂模块的中分辨率x射线结构分析中，所有四种蛋白质都仅被建模为聚丙氨酸。我的初步工作强烈表明，ACPM1的一部分分别与参与Fe-S簇生物发生的LYRM4(ISD11)-NFS1复合体共存，并作为自由基质蛋白（matrix-ACPM1）共存。ACPM1-LYRM4/NFS1配合物的分离与本文提出的新型多组分硫辛酸合成配合物一致。与复合物I亚基acpm （CI-ACPM）相比，基质-ACPM1是n端乙酰化的，这表明亚线粒体分选机制将ACPM1分配给基质或复合物I。初始质谱数据表明，部分基质-ACPM1携带一个新兴脂肪酸链（c9 - c16 -酰基-ACPM1中间体）。我们在CI-ACPM1和CI-ACPM2上发现了更高质量的酰基，但它们的身份尚不清楚。该项目的主要重点将是揭示基质- acpm1的功能，并解决ACPM1-LYRM4/NFS1复合物在硫辛酸合成中的作用。我的目标是了解ACPM1与线粒体复合体I和NFS1复合体的关联，而实现这一目标的重要一步将是识别结合的酰基。ACPM1、LYRM6和ACPM1- lyrm4 /NFS1复合体的结构测定将揭示ACPM1锚定在lyrm上的分子基础，并有望提供重要线索，说明ACPM-LYRM结构域的存在对复合体I和NFS1蛋白的功能至关重要。

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.