21416
FKBP16 - 3s are well conserved in eukaryotic photosynthetic organisms , including the presence of a unique disulfide - forming CxxxC motif in their N - terminal regions .
 disulfide, N
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 disulfide, N