4007
All conserved cysteine and arginine residues in this domain were mutated by site-directed mutagenesis , and the mutant proteins were characterized by blocking reactions , ligand-binding experiments , transactivation assays , and protease mapping .
 ( protein: protease, None) , ( protein: mutant proteins, None) 
Locate the role in the text that participated in the event based on the event type and return it in the event list. 
 Option: Event type: RNA,cell type,protein,cell line,DNA, Arguments type: . 
Text: {0} 
Answer:
 ( protein: protease, None) , ( protein: mutant proteins, None) 