13403
Feasibility of this recombinant approach was explored with a focus on Drosophila bursicon , a heterodimeric cystine - knot protein that activates the G protein - coupled receptor rickets ( rk ) .
 Chemical: cystine
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
 Chemical: cystine