Immunogen sequence: DHTKPCWYWD KKDLAHTPSQ LEGLDPATEA RYRREGARFI FDVGTRLGLH YDTLATGIIY FHRFYMFHSF KQFPRYVTGA CCLFLAGKVE ETPKKCKDII KTARSLLNDV QFGQFGDDPK EEVMVLERIL LQTIKFDLQV EHPYQFLL. Regulatory subunit of cyclin-dependent kinases that mediates activatio