the team of researchers used native selenomethionine-containing protein that yielded crucial crystal forms. ns2 pro (non-structural protease) monomer is made up of two sub-domains which is connected by a linker. each monomer contains the anti-parallel alpha-helices and a loop of beta strands. ns2 dimer consists of two monomers each facing their n and c-termini toward each other. n-termini stay in close proximity while c-termini are farther apart from each other which resembles ‘butterfly’. ns2-3 protease is 42 kda in length. earlier studies also suggested that it was almost impossible to isolate ns2-3 protease due to hydrophobic nature of the native ns2.