Functional annotation and evaluation of hypothetical proteins in cyanobacterium Synechocystis sp. PCC 6803

Abstract

The cyanobacterium Synechocystis sp. PCC 6803 is well reported as a potential species for producing valuable bioactive compounds as well as model microorganism for investigating photosynthesis. However, there are a great number of proteins in the genome of this microorganism with unclear functions. To this end, the present study employed numerous bioinformatics techniques in conjunction with experimental validation to describe the function of four hypothetical proteins in cyanobacterium Synechocystis sp. PCC 6803. Four potential proteins, namely sll1388, sll1512 (cytosolic), sll1164, and slr0964 (membrane), were selected for functional annotation. The sll1388 and sll1512 proteins containing adenosine triphosphate (ATP) and deoxyribonucleic acid (DNA) are expected to be induced by toxic concentrations of NaCl and hydrogen peroxide (H2O2). Sll1164 and slr0964 are predicted as membrane proteins involved in cysteine (Cys) and ferrous (Fe2+) transport. The Adaptive Poisson-Boltzmann Solver (APBS) findings suggested negative and positive charges for ligand-binding sites and negative and uncharged residues for predicted pores. Transcript levels of sll1388 and sll1512 increased at high concentrations of NaCl and H2O2. An increase in the expression level of sll1164 and slr0964 was observed under Sulfur (S) and Fe2+ depletion. Transcript analysis along with experimental gene expression research gave us vital indications concerning the function of the above-mentioned hypothetical proteins. The present study used a combination of in silico approaches in conjugation with experimental methods, which finally increased our understanding of the stress tolerance of Synechocystis sp. PCC 6803 as a potential model microorganism with industrial applications.