Supplementary Material S1: Strategy to construct barnase gene with PstI site A PstI site was introduced in the barnase gene by mutating the ‘T’ base at the 45th position to a ‘G’ creates the site ‘CTGCAG’. Further, CTT and CTG both encode for the same amino acid, i.e. lysine. In the present study we modified barnase gene sequence by creating two adjacent PstI sites separated by four nucleotides so that the modified barnase gene is not able to synthesize any functional protein. This was done for ease in cloning of the modified barnase gene without the need to express the barstar protein. The modified barnase gene was synthesized by Splicing by overlap extension (SOE) method (Horton, 1993). This PCR method is used either to insert mutation at specific positions or to splice smaller DNA fragments into a single larger fragment. The overall strategy is outlined in the figure below. The gene was synthesized in two parts. The initial 63 base pairs were made by annealing the sense and the antisense strand which were commercially synthesized. The sequence of the oligonucleotide strands and primers is given in the Table below. This fragment also carried the base change and the additional 10 base pairs to create the two PstI sites. The rest of the gene was amplified using a forward and a reverse primer F1 and R1. The F1 primer carried a region overlapping with the fragment synthesized by annealing. The two fragments were assembled by SOEing PCR and the product was finally amplified by using primers F2 and R2. The amplified product of 346bp was cloned in pCR® Blunt-II-TOPO® vector and then sequenced. Table: Sequence of oligonucleotides and primers used for the synthesis of modified barnase by (SOE) PCR. S.No. Oligonucleotide/Primer Sequence (5'-3') 1. Sense strand 5'-AAT CCA TGG CAC AGG TTA TCA ACA CGT TTG ACG GGG TTG CGG ATT ATC TGC AGA ATT CTG CAG-3' 2. Antisense strand 5’-CTG CAG AAT TCT GCA GAT AAT CCG CAA CCC CGT CAA ACG TGT TGA TAA CCT GTG CCA TGG ATT-3‘ 3. Forward primer (F1) 5'- GAT TAT CTG CAG AAT TCT GCA GAC ATA TCA TAA GCT ACC-3' 4. Reverse primer (R1) 5'- ATA TCT AGA TTA TCT GAT TTT TGT AAA GGT CTG ATA ATG GTC CG-3' 5. Forward primer (F2) 5'-GCT CCA TGG CAC AGG TTA TCA ACA CGT T-3' 6. Reverse primer (R2) 5'- ATA TCT AGA TTA TCT GAT TTT TGT AAA GGT CTG ATA ATG GTC CG-3'