passages.id: split_4_test_538_passage
passages.type: progene_text
passages.text: Cryo-EM has shown that the integrin - binding RGD ( Arg - Gly - Asp ) protrusion of the Ad2 penton base protein is highly mobile ( P. L. Stewart , C. Y. Chiu , S. Huang , T. Muir , Y. Zhao , B. Chait , P. Mathias , and G. R. Nemerow , EMBO J. 16 : 1189 - 1198 , 1997 ) .