11813
An F222W : W21F rGST A1 - 1 double mutant provides a direct fluorescence probe of changes in the environment of the C - terminal residue .
 F222W : W21F rGST A1 - 1 double mutant
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: GENE 
Text: {0} 
Answer:
 F222W : W21F rGST A1 - 1 double mutant