Annotation of a hypothetical protein in space exposed Bacillus pumilus SAFR_032 bacteria as Thioredoxin and structural analysis of the mutations

Abstract: Bacillus pumilus strain SAFR_032 is a spore forming bacteria that survived and showed high resistance when exposed to real space conditions (International space station). The space conditions included heat, ultraviolet, gamma, and cosmic radiations, desiccation and microgravity. Though the genome of space-exposed B.pumilus SAFR_032 was sequenced some genes like BPUM_0788 and others were designated as hypothetical proteins . Using BLAST and domain databases we annotated BPUM_0788 gene as Thioredoxin gene, which is responsible for regulation of thioredoxin (TRX family) protein having oxidoreductase activity, peroxide resistance and oxidative stress response. These functions are known to help overcome stressful conditions. Comparison of BPUM_0788 with its counterpart from Bacillus pumilus ATCC 7061 ground control in EMBOSS needle - pairwise alignment revealed three mutations specific to the space- exposed strain. These mutations are Alanine 83 serine (A83S), Glutamic acid 129 aspartic acid(E129D) and Aspartic acid 145 asparagine(D145N). Alpha fold 2 was used to model the structure of the protein. The functional and structural implications of these mutations were analyzed using domain search, STRING database and DynaMut2. Dynamut2 showed a destabilizing effect of all the three mutations. We hypothesize that these mutations may be helpful in thioredoxin to cope up with the stressful conditions experienced in space exposure. These methods can be used to annotate and analyse many remaining hypothetical proteins in the same and other bacteria.

Keywords: Bacillus pumulis SAFR_032, Hypothetical protein, Thioredoxin, gene annotation, mutation, space exposed stress