拟南芥ROOTUV-B敏感1和2与氨基转移酶相互作用，调节维生素B6稳态
吡哆醛-5'-磷酸酯(PLP)是维生素B6(vitB6)的酶促辅因子形式，是一种在代谢中起重要作用的多用途化合物。细胞PLP的稳态调节目前还不是很清楚。
本文报道了在拟南芥中，生物合成的PLP被特异的氨基转移酶(ATs)所固定，并且UV-B敏感蛋白RUS1和RUS2与ATs一起作用，调节PLP的稳态。rus1和rus2突变体生长发育不良的表型以前被证明是可以被外源供应的VitB6挽救的。天冬氨酸氨基转移酶2(ASP2)中PLP结合袋附近的特定残基变化也拯救了rus1和rus2表型。在本研究中，饱和抑制子筛选在4个转氨酶基因(ASP1、ASP2、ASP3或丙氨酸氨基转移酶1(AAT1))中发现了14个rus抑制子(sor)等位基因，它们对rus表型有不同程度的抑制作用。每一个sor突变都改变了蛋白质PLP结合口袋中的一个氨基酸，并且sor蛋白质被发现具有降低的PLP结合水平。
遗传数据表明PLP的可用性通常需要RUS1和RUS2，并且增加sor突变体的数量会增加rus表型的抑制。生化结果表明，RUS1和RUS2与ATS有物理相互作用。我们的研究提示RUS1、RUS2和特异性ATs共同调控拟南芥PLP稳态的机制。
Pyridoxal-5'-phosphate (PLP), the enzymatic cofactor form of Vitamin B6 (vitB6), is a versatile compound that has essential roles in metabolism. Cellular PLP homeostasic regulation is currently not well understood. Here we report that in Arabidopsis, biosynthesized PLP is sequestered by specific aminotransferases (ATs), and that the proteins ROOT UV-B SENSITIVE 1 (RUS1) and RUS2 function with ATs to regulate PLP homeostasis. The stunted growth phenotypes of rus1 and rus2 mutants were previously shown to be rescuable by exogenously supplied vitB6. Specific residue changes near the PLP-binding pocket in ASPARTATE AMINOTRANSFERASE2 (ASP2) also rescued rus1 and rus2 phenotypes. In this study, saturated suppressor screens identified 14 additional suppressor of rus (sor) alleles in four aminotransferase genes (ASP1, ASP2, ASP3, or ALANIN AMINOTRANSFERASE1 (AAT1)), which suppressed the rus phenotypes to varying degrees. Each of the sor mutations altered an amino acid in the PLP-binding pocket of the protein, and sor proteins were found to have reduced levels of PLP conjugation. Genetic data revealed that the availability of PLP normally requires both RUS1 and RUS2, and that increasing the number of sor mutants additively enhanced the suppression of rus phenotypes. Biochemical results showed that RUS1 and RUS2 physically interacted with ATs. Our studies suggest a mechanism in which RUS1, RUS2 and specific ATs work together to regulate PLP homeostasis in Arabidopsis.
doi:
https://doi.org/10.1101/2021.03.01.433438
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