Suzuki Tomohiro, Tomita Takeo, Hirayama Kenta, Suzuki Michio, Kuzuyama Tomohisa, Nishiyama Makoto
Biotechnology Research Center, The University of Tokyo, Japan.
Collaborative Research Institute for Innovative Microbiology, The University of Tokyo, Japan.
FEBS J. 2021 Mar;288(6):1975-1988. doi: 10.1111/febs.15527. Epub 2020 Sep 8.
Homocitrate synthase (HCS) catalyzes the aldol condensation of α-ketoglutarate and acetyl coenzyme A to form homocitrate, which is the first committed step of lysine biosynthesis through the α-aminoadipate pathway in yeast, fungi, and some prokaryotes. We determined the crystal structure of a truncated form of HCS from a hyperthermophilic acidophilic archaeon, Sulfolobus acidocaldarius, which lacks the RAM (Regulation of amino acid metabolism) domain at the C terminus serving as the regulatory domain for the feedback inhibition by lysine, in complex with α-ketoglutarate, Mg , and CoA. This structure coupled with mutational analysis revealed that a subdomain, subdomain II, connecting the N-terminal catalytic domain and C-terminal RAM domain is involved in the recognition of acetyl-CoA. This is the first structural evidence of the function of subdomain II in the related enzyme family, which will lead to a better understanding of the catalytic mechanism of HCS. DATABASES: Structural data are available in the RCSB PDB database under the accession number 6KTQ.
同柠檬酸合酶（HCS）催化α-酮戊二酸和乙酰辅酶A的羟醛缩合反应形成同柠檬酸，这是酵母、真菌和一些原核生物中通过α-氨基己二酸途径进行赖氨酸生物合成的第一个关键步骤。我们确定了来自嗜热嗜酸古菌嗜酸热硫化叶菌的截短形式HCS的晶体结构，该截短形式在C端缺少作为赖氨酸反馈抑制调节结构域的RAM（氨基酸代谢调节）结构域，它与α-酮戊二酸、Mg²⁺和辅酶A形成复合物。该结构与突变分析表明，连接N端催化结构域和C端RAM结构域的一个亚结构域，即亚结构域II，参与了对乙酰辅酶A的识别。这是相关酶家族中亚结构域II功能的首个结构证据，这将有助于更好地理解HCS的催化机制。数据库：结构数据可在RCSB PDB数据库中获取，登录号为6KTQ。
