... activation site (R144, N154, I152) and three in thesecond (F127, M436 and H428), and found that Ap4A and ADP interactwith the same site, but the sites for ATP and BPG remain uncertain. Thestructural ... cN-II, cN-III, cN-IA and cN-IB, and both cytosolic and mitochondrial 5¢(3¢)-deoxyribonu-cleotidases [5]. Even though all soluble 5 ¢-nucleotidasesshare the same reaction mechanism and possess con-served ... R144E,N154D, K311A, G319D, D396A and M436W wereobtained using the PCR-based site-directed mutagenesismethod described by Fisher and Pei [18], and the pointmutants Y55G, T56V and H428D were produced...