passages.id: split_5_test_1478_passage
passages.type: progene_text
passages.text: The precise orientation of key residues ( Arg ( 454 ) , Tyr(456) , Cys(472) , Gly ( 488 ) , Thr(491) , and Trp(677) ) has been defined by x - ray crystallography ( Wang , M. , Roberts , D. L. , Paschke , R. , Shea , T. M. , Masters , B. S. , Kim , J. - J. P. ( 1997 ) Proc. Natl. Acad. Sci. U. S. A. 94 , 8411 - 8416 ) .