of E. coli ATCase (2) suggests that the lower stability could be due, at least in part, to the loss of charged interactions between regulatory subunits (r1-r6) and between regulatory and catalytic subunits (r1-c1). The absence of ATP activation could result from a modification not in the effector site (which is conserved) but rather along the path followed by the transmission of the allosteric signal.
1. Liang, Z., Demarez, M., Legrain, C., Baetens, M., Glansdorff, N., Ruger, H.J., and Tan, T.L. (1996) Arch. Physiol. Biochem., 104, B15.
2. Gouaux, J.E. and Lipscomb, W.N. (1990) Biochemistry, 29, 389-402.
