3719
This result suggests that the target protein specificity of E2s can be altered by the addition of appropriate C - terminal extensions , thus providing a way to modify the selectivity of the ubiquitin system .
 GENE: E2s; GENE: ubiquitin
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: GENE 
Text: {0} 
Answer:
 GENE: E2s; GENE: ubiquitin