ANALYSIS OF Mycobacterium smegmatis’ METABOLISM MODULATION: CHARACTERIZATION OF PII PROTEIN ROLE

ENSINCK D; GAGO G; HUERGO L; GRAMAJO H; DIACOVICH L

Congreso; SAIB 2021; 2021

ANALYSIS OF Mycobacterium smegmatis METABOLISM MODULATION: CHARACTERIZATION OF PII PROTEIN ROLEEnsinck D1, Gago G1, Huergo L2, Gramajo H1, Diacovich L1 1 Instituto de Biología Celular y Molecular de Rosario (IBR), Argentina, 2 Instituto Nacional de Ciência e Tecnologia da Fixação Biológica de Nitrogênio, Brasil. E-mail: ensinck@ibr-conicet.gov.arMycobacteria possess a versatile metabolism, which allows them to adapt and survive within their hosts. Unveiling the complex network that coordinates the different metabolisms would provide us with valuable information for the efforts to end tuberculosis. In other bacteria, such as Escherichia coli, PII proteins have been positioned as one of the links between nitrogen and carbon metabolism. This family of signal transduction protein sense α-ketoglutarate, ATP and ADP, which are indicators of the carbon, nitrogen and energy status. The different conformational-states, determined by the union of these allosteric effectors, leads to the interaction with a specific group of target proteins, mainly of which are involved in nitrogen assimilatory pathway. Furthermore, in some organisms, GlnB orthologs (members of the PII family) modulate carbon metabolism by interacting with the acetyl-CoA carboxylase complex and reducing its activity. Nitrogen starvation has been shown to induce expression of the PII protein in mycobacteria, including the pathogen Mycobacterium tuberculosis, however, it role has not been described. Previous results from our laboratory demonstrated that PII is a non-essential protein for Mycobacterium smegmatis, since its deletion mutant is capable of growing in media containing limiting levels of ammonia. In this work, we show that PII mutant does not exhibit growth differences to the wild type strain when given an ammonia shock after being deprived of nitrogen nor when nitrate is used as the sole nitrogen source. When this strain was cultured on nitrite, the mutant exhibited a prolonged lag phase compared to the wild-type strain and reached lower optical densities. This effect wasexacerbated when the nitrite concentration was increased. This result suggest that PII may be involved in nitrite assimilation and/or detoxification. Regarding the modulation of carbon metabolism, PII proteins do not regulate the acyl-CoA activity in mycobacteria, as there is not modification in acetyl-CoA and propionyl-CoA activity in protein extracts of M. smegmatis grown in an ammonia limiting condition, and after an ammonia shock. Further research is required for a better understanding of PII role in these organisms.