Bioinformatics analysis of enzymes involved in cysteine biosynthesis: first evidence for the formation of cysteine synthase complex in cyanobacteria.

The biosynthesis of cysteine is crucial and critically regulated by two enzymes. i.e., serine acetyl transferase (SAT) and O-acetyl serine (thiol) lyase (OAS-TL). A descriptive account on the activity and regulatory mechanism of the enzyme is available in bacteria and plants. But no such studies yet performed in cyanobacteria, to understand the evolutionary aspect of cysteine biosynthesis and its regulation. Therefore, in our study a detailed bioinformatic analysis has been performed to understand all the possible features of cyanobacterial SATs and OAS-TLs. The analysis of SAT and OAS-TL sequences from cyanobacteria depicted that the large genome and morphological complexities favoured acquisition of these genes. Besides, conserved function of these enzymes was presumed by their sequence similarity. Further, the phylogenetic tree consisted of distinct clusters for unicellular, filamentous, and heterocytous strains. Nevertheless, the specificity pocket, SVKDR for OAS-TL having K as catalytic residue was also identified. Additionally, in silico protein modelling of SAT (SrpG) and OAS-TL (SrpH) of Synechococcus elongatus PCC 7942 was performed to gain insight into the structural attributes of the proteins. Finally, here we showed the possibility of hetero-oligomeric bi-enzyme cysteine synthase complex formation upon interaction of SAT and OAS-TL through protein-protein docking analysis thus provides a way to understand the regulation of cysteine biosynthesis in cyanobacteria. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s13205-021-02899-1. © King Abdulaziz City for Science and Technology 2021.