Análises in silico de metalotioneínas (MTs) e a tolerância de Panagrolaimus superbus à hipóxia por imersão em matriz metálica de Gálio

Abstract

In silico analysis of metallothioneins (MTs) and the tolerance of Panagrolaimus superbus to hypoxia by immersion in a Gallium matrix. The free-living nematode Panagrolaimus superbus is able to enter into a state of suspended animation when exposed to extreme desiccation-phenomenon known as anhydrobiosis (life without water). During the dry state, anhydrobiotic organisms tolerate several physical stresses, such as extremes of temperature, vacuum and hyperacceleration. Metallothioneins (MTs) are ubiquitous proteins with short chains, capable of acting on detoxification and homeostasis of heavy metals due to the high content of cysteines in their chains. Considering that desiccated anhydrobiotic organisms remain viable for long periods in dry soils, in which high concentrations of metal ions are exhibited, we hypothesized that these organisms show tolerance to heavy metals due to structural differences in their MTs. Therefore, the objectives of this work were to investigate the tolerance of P. superbus to complete immersion in Gallium (Ga), by analyzing its viability and population growth, and to identify structural differences in MTs between anhydrobiotic and non-anhydrobiotic organisms by performing in silico analyses (cysteine composition and conservation, structural modeling, primary and tertiary structure analyses and alignment, and ligand affinity). The results demonstrate the high tolerance of P. superbus to hypoxic confinement in Ga for 7 days, with no negative effects on its viability and population growth. Additionally, the results of in silico analyses show higher values of cysteine composition and conservation in nonanhydrobiotic MTs, but no differences in tertiary structures and ligand interactions were shown. Thus, we report for the first time the preservation of an anhydrobiotic organism inside a heavy metal matrix. However, we suggest that this anhydrobiosis-mediated tolerance is not conferred by structural differences in MTs, but by their differential gene expression and/or involve a set of elements of the anhydrobiosis repair machinery.