passages.id: split_8_test_1299_passage
passages.type: progene_text
passages.text: Based on computer alignments , the RUB NS protease was predicted to be a papain - like cysteine protease ( PCP ) with the residues Cys1152 and His1273 as the catalytic dyad ; however , the RUB NS protease was recently found to require divalent cations such as Zn , Co , and Cd for activity ( X. Liu , S. L. Ropp , R. J. Jackson , and T. K. Frey , J. Virol. 72 : 4463 - 4466 , 1998 ) .