5453
Recombinant c-Jun and c-Fos were ubiquitinylated by the ubiquitin carrier enzymes E214K , E220K , or E232K in the presence of the ubiquitin-activating enzyme , E1 .
 c-Jun, ubiquitin-activating enzyme, c-Fos, ubiquitin carrier enzymes, E220K, E1, E232K, E214K
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: cell line, protein, RNA, DNA, cell type 
Text: {0} 
Answer:
 c-Jun, ubiquitin-activating enzyme, c-Fos, ubiquitin carrier enzymes, E220K, E1, E232K, E214K