Peculiar Endosymbiosis in the Cyanobiont Nostoc azollae 0708: An In Silico Approach

Nostoc azollae 0708 exhibits peculiar endosymbiosis owing to the unique commitment of cyanobiont’s association with fern throughout its life cycle. This chapter elaborates various in silico approaches adopted for intriguing proteomics aspects of Fe and Mn superoxide dismutase in the cyanobiont Nostoc azollae 0708. Prediction of physicochemical parameters elucidating molecular weight, isoelectric point (pI), instability index, aliphatic index, total no. of negatively charged residues (Asp + Glu), total no. of positively charged residues (Arg + Lys), extinction coefficient, and GRAVY are discussed in detail. Generating good quality 3D structural models for Fe-SOD and Mn-SOD by homology modeling and validation by Prosa-web, verify-3D, and PROCHECK is elaborately explained. Conservation of metal binding positions, domains, and motifs suggesting functional conservation, highly conserved exposed as well as buried amino acid residues advocating their structural and functional importance is also discussed. Generation of protein–protein interaction network using STRING illustrating the physical and functional interaction of superoxide dismutase with other proteins and biological cascade of these proteins in Nostoc azollae has been described. The NJ phylogenetic tree for Fe-SOD depicts Nostoc sp. PCC 7524 as the nearest evolutionary homolog, whereas Nostoc sp. PCC 7107 and Nostoc piscinale CENA 21 as evolutionary close homologs of Mn-SOD in Nostoc azollae. The present in silico methodologies discussed in this chapter may pave the way for further experimental validation aiding in exploring the biochemical, biotechnological, and biofertilizer potential of the cyanobiont recruited by the fern Azolla.