Aparecida Gonçalves Ana Carolina, de Mello Damasco Nunes Tatiana, Parize Erick, Marques Gerhardt Edileusa Cristina, Antônio de Souza Gustavo, Scholl Jörg, Forchhammer Karl, Huergo Luciano Fernandes
Setor Litoral, UFPR Matinhos, Paraná, Brazil.
Programa de Pós-Graduação em Ciências - Bioquímica, UFPR Curitiba, Paraná, Brazil.
J Biol Chem. 2024 Dec;300(12):107931. doi: 10.1016/j.jbc.2024.107931. Epub 2024 Oct 24.
The PII signaling proteins are ubiquitous in prokaryotes serving as crucial metabolic hubs in different metabolic pathways because of their ability to sense and integrate signals of the cellular nitrogen, carbon, and energy levels. In this study, we used ligand fishing assays to identify the ribonucleotide monophosphatase UmpH enzyme as a novel target of the PII signaling protein GlnK in Escherichia coli. In vitro analyses showed that UmpH interacts specifically with the PII protein GlnK but not with its paralog protein GlnB. The UmpH-GlnK complex is modulated by the GlnK uridylylation status and by the levels of the GlnK allosteric effectors ATP, ADP, and 2-oxoglutarate. Upon engaging interaction with GlnK, UmpH becomes less active toward its substrate uridine 5'-monophosphate. We suggest a model where GlnK will physically interact to reduce the UmpH activity during the transition from N-starvation to N-sufficient conditions. Such a mechanism may help the cells to reprogram the fate of uridine 5'-monophosphate from catabolism to anabolism avoiding futile cycling of key nutrients.
PII信号蛋白在原核生物中普遍存在，由于其能够感知和整合细胞氮、碳和能量水平的信号，因而在不同的代谢途径中充当关键的代谢枢纽。在本研究中，我们使用配体垂钓分析，确定核糖核苷酸单磷酸酶UmpH酶是大肠杆菌中PII信号蛋白GlnK的一个新靶点。体外分析表明，UmpH与PII蛋白GlnK特异性相互作用，但不与其旁系同源蛋白GlnB相互作用。UmpH-GlnK复合物受GlnK尿苷酰化状态以及GlnK变构效应物ATP、ADP和2-酮戊二酸水平的调节。与GlnK相互作用后，UmpH对其底物尿苷5'-单磷酸的活性降低。我们提出了一个模型，即在从氮饥饿到氮充足的转变过程中GlnK将通过物理相互作用降低UmpH活性。这样一种机制可能有助于细胞重新规划尿苷5'-单磷酸从分解代谢到合成代谢的命运，避免关键营养物质的无效循环。
