406
These results suggest that (1) the differentiation inhibitory activity of I-factor /nm23 protein is not restricted to monocytic differentiation of M1 cells , (2) the inhibitory activity is exhibited without species specificity, and (3) the differentiation inhibitory activity of the nm23/NDP kinase protein is independent of its enzyme activity and requires the presence of N-terminal peptides .
 ( protein: nm23/NDP kinase protein, None) , ( cell line: M1 cells, None) , ( protein: I-factor, None) , ( protein: I-factor /nm23 protein, None) 
Locate the role in the text that participated in the event based on the event type and return it in the event list. 
 Option: Event type: RNA,cell type,protein,cell line,DNA, Arguments type: . 
Text: {0} 
Answer:
 ( protein: nm23/NDP kinase protein, None) , ( cell line: M1 cells, None) , ( protein: I-factor, None) , ( protein: I-factor /nm23 protein, None) 