Children's Hospital Oakland Research Institute, Oakland, California, United States of America.
Institute of Human Genetics, Medical University Innsbruck, Innsbruck, Austria.
PLoS One. 2020 Feb 27;15(2):e0229718. doi: 10.1371/journal.pone.0229718. eCollection 2020.
Glycine N-myristoylation is an essential acylation modification modulating the functions, stability, and membrane association of diverse cytosolic proteins in human cells. Myristoyl-CoA is the 14-carbon acyl donor of the acyltransferase reaction. Acyl-CoAs of a chain length compatible with the binding site of the N-myristoyltransferase enzymes (NMT) are competitive inhibitors, and the mechanism protecting these enzymes from unwanted acyl-CoA species requires the acyl-CoA binding protein ACBD6. The acyl-CoA binding domain (ACB) and the ankyrin-repeat motifs (ANK) of ACBD6 can perform their functions independently. Interaction of ANK with human NMT2 was necessary and sufficient to provide protection. Fusion of the ANK module to the acyl-CoA binding protein ACBD1 was sufficient to confer the NMT-stimulatory property of ACBD6 to the chimera. The ACB domain is dispensable and sequestration of the competitor was not the basis for NMT2 protection. Acyl-CoAs bound to ACB modulate the function of the ANK module and act as positive effector of the allosteric activation of the enzyme. The functional relevance of homozygous mutations in ACBD6 gene, which have not been associated with a disease so far, is presented. Skin-derived fibroblasts of two unrelated individuals with neurodevelopmental disorder and carrying loss of function mutations in the ACBD6 gene were deficient in protein N-myristoylation. These cells were sensitive to substrate analog competing for myristoyl-CoA binding to NMT. These findings account for the requirement of an ANK-containing acyl-CoA binding protein in the cellular mechanism protecting the NMT enzymes and establish that in human cells, ACBD6 supports the N-myristoylation of proteins.
甘氨酸 N-豆蔻酰化是一种必需的酰化修饰，可调节人类细胞中各种细胞质蛋白的功能、稳定性和膜结合。豆蔻酰-CoA 是酰基转移酶反应的 14 碳酰基供体。链长与 N-豆蔻酰转移酶酶（NMT）结合位点兼容的酰基辅酶 A 是竞争性抑制剂，保护这些酶免受不需要的酰基辅酶 A 物质的机制需要酰基辅酶 A 结合蛋白 ACBD6。ACBD6 的酰基辅酶 A 结合域（ACB）和锚蛋白重复基序（ANK）可以独立发挥作用。ANK 与人类 NMT2 的相互作用对于提供保护是必要和充分的。ANK 模块与酰基辅酶 A 结合蛋白 ACBD1 的融合足以赋予嵌合体 NMT 的刺激特性 ACBD6。ACB 结构域是可有可无的，并且竞争者的隔离不是 NMT2 保护的基础。与 ACB 结合的酰基辅酶 A 调节 ANK 模块的功能，并作为酶变构激活的正效应物。迄今为止，尚未与疾病相关的 ACBD6 基因突变的同源突变体的功能相关性被提出。携带 ACBD6 基因突变且具有神经发育障碍的两个无关个体的皮肤衍生成纤维细胞缺乏蛋白质豆蔻酰化。这些细胞对竞争结合 NMT 的豆蔻酰-CoA 的底物类似物敏感。这些发现解释了含有 ANK 的酰基辅酶 A 结合蛋白在保护 NMT 酶的细胞机制中的必要性，并确立了在人类细胞中，ACBD6 支持蛋白质的豆蔻酰化。
