6540
PTP - S3 differs from PTP - S4 in having a deletion of 19 amino acids corresponding to exon E1 .
 PTP - S3, PTP - S4
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: GENE 
Text: {0} 
Answer:
 PTP - S3, PTP - S4