Research Institute, National Cancer Center, Goyang, 10408, Republic of Korea.
Division of Medical Sciences, College of Medicine, Yonsei University, Seoul, 03722, Republic of Korea.
Sci Rep. 2023 Dec 15;13(1):22326. doi: 10.1038/s41598-023-49332-6.
Isozymes are enzymes that catalyze identical biological reactions, yet exhibit slight variations in structures and catalytic efficiency, which enables the precise adjustment of metabolism to fulfill the specific requirements of a particular tissue or stage of development. Methionine aminopeptidase (MetAP) isozymes function a critical role in cleaving N-terminal methionine from nascent proteins to generate functional proteins. In humans, two distinct MetAP types I and II have been identified, with type I further categorized into cytosolic (MetAP1) and mitochondrial (MetAP1D) variants. However, despite extensive structural studies on both bacterial and human cytosolic MetAPs, the structural information remains unavailable for human mitochondrial MetAP. This study was aimed to elucidate the high-resolution structures of human mitochondrial MetAP1D in its apo-, cobalt-, and methionine-bound states. Through a comprehensive analysis of the determined structures and a docking simulation model with mitochondrial substrate peptides, we present mechanistic insights into the cleavage process of the initiator methionine from mitochondrial proteins. Notably, despite the shared features at the active site between the cytosolic and mitochondrial MetAP type I isozymes, we identified distinct structural disparities within the active-site pocket primarily contributed by two specific loops that could play a role in accommodating specific substrates. These structural insights offer a basis for the further exploration of MetAP isozymes as critical players in cellular processes and potential therapeutic applications.
同工酶是能够催化相同生物反应的酶，但它们的结构和催化效率略有不同，这使得代谢能够精确地调整以满足特定组织或发育阶段的特定需求。甲硫氨酸氨肽酶（MetAP）同工酶在从新生蛋白质中切割 N 端甲硫氨酸以产生功能蛋白方面起着关键作用。在人类中，已经鉴定出两种不同的 MetAP 类型 I 和 II，其中类型 I 进一步分为胞质（MetAP1）和线粒体（MetAP1D）变体。然而，尽管对细菌和人类胞质 MetAP 进行了广泛的结构研究，但人类线粒体 MetAP 的结构信息仍然未知。本研究旨在阐明人线粒体 MetAP1D 在apo、钴和甲硫氨酸结合状态下的高分辨率结构。通过对确定结构的全面分析以及与线粒体底物肽的对接模拟模型，我们提出了关于线粒体蛋白起始甲硫氨酸切割过程的机制见解。值得注意的是，尽管胞质和线粒体 MetAP 类型 I 同工酶的活性位点具有共同特征，但我们在活性口袋内发现了明显的结构差异，主要归因于两个特定环，它们可能在容纳特定底物方面发挥作用。这些结构见解为进一步探索 MetAP 同工酶作为细胞过程中的关键参与者以及潜在的治疗应用提供了基础。
