... D and E + F), (b) a few hydrogen bonds, and a hydrophobic interaction between A + C,B + E and D + F, and (c) electrostatic forces in thecentral channel of the hexamer between B, C and F, and ... side chain of Asp70, and onefrom the backbone N of Gly63, and the phosphategroup forming hydrogen bonds from O1 to Arg55,from O2 to the backbone N and the side chain of Thr138, and from O3 ... F133N and F133A, were expressed, purified and characterized.With 1 mm UMP and ATP as substrates, the activities of F133N and F133A were only 50 and 20% of that of the wild-type enzyme. Similar to...