MULTIDRUG-RESISTANCE PROTEIN (MDR)-ALKALINE PHOSPHATASE HYBRIDS IN ESCHERICHIA-COLI SUGGEST A MAJOR REVISION IN THE TOPOLOGY OF THE C-TERMINAL HALF OF MDR
O. Beja et E. Bibi, MULTIDRUG-RESISTANCE PROTEIN (MDR)-ALKALINE PHOSPHATASE HYBRIDS IN ESCHERICHIA-COLI SUGGEST A MAJOR REVISION IN THE TOPOLOGY OF THE C-TERMINAL HALF OF MDR, The Journal of biological chemistry, 270(21), 1995, pp. 12351-12354
Recent studies reveal that the organization of the multidrug resistanc
e protein (Mdr) in the membrane is probably not exactly as predicted f
rom hydropathy profiling, When expressed in Escherichia coli, phoA gen
e fusions can be utilized to study the membrane topology of Mdr. Using
this approach, it was proposed recently that the N-terminal hydrophob
ic domain of Mdr spans the membrane six times, in a different fashion
from that predicted by hydropathy analysis (Bibi, E. and Beja, O. (199
4) J. Biol. Chem. 269, 19910-19915). In this study, we analyze mdr-pho
A fusions constructed in the C-terminal half of Mdr. Overall, the resu
lts presented here lead to a significant revision in the membrane topo
logy model of the C-terminal half of Mdr. The new topology is discusse
d with regard to the hydropathy profiles of the well characterized ABC
proteins MalG and MalF, which are strikingly similar to those of the
N- and C-terminal halves of Mdr, respectively.