JBC, Vol. 250, Issue 10, 3666-3671, May, 1975
Deoxycytidine transport in the presence of a cytidine deaminase inhibitor and the transport of uracil in Escherichia coli B
P. J. von Dippe, K. Leung, S. Roy-Burman and D. W. Visser
Tetrahydrouridine, a cytidine deaminase inhibitor, prevents periplasmic
degradation of deoxycytidine by Escherichia coli B. It does not inhibit
deoxycytidine transport and therefore allows an accurate determination of
deoxycytidine transport. Data obtained using tetrahydrouridine show that
deoxycytidine is transported in E. coli B as the intact nucleoside by an
active transport process, with a K-m of 6 times 10-minus 6 M. Cytidine and
deoxyadenosine inhibit transport competitively, whereas guanosine has no
effect on transport. Arsenate or KCN greatly reduces transport. In a mutant
resistant to the nucleoside antibiotic, showdomycin, the active transport
of deoxycytidine is lost, and residual slow uptake occurs by passive
diffusion. Uracil is accumulated in E. coli B by an active transport
process with a K-m of 5 times 10-minus 7 M.