This article has been retracted at the request of the authors. Please see .
Reason: The recently reported structure of Sav1866 (4) indicated that our MsbA structures (1–3) were incorrect in both the hand of the structure and the topology. Thus, the biological interpretations based on the inverted models for MsbA are invalid.
An in-house data reduction program introduced a change in sign for anomalous differences. This program, which was not part of a conventional data processing package, converted the anomalous pairs (I+ and I−) to (F− and F+), thereby introducing a sign change. As the diffraction data collected for each set of MsbA crystals (1–3) were processed with the same program, the structures reported had the wrong hand.
The error in the topology of the original MsbA structure was a consequence of the lower resolution of the data as well as breaks in the electron density for the connecting loop regions. Unfortunately, the use of the multicopy refinement procedure allowed us to obtain reasonable refinement values for the wrong structures.
The Protein Data Bank (PDB) file 1PF4 has been moved to the archive of obsolete PDB entries. The structures will be recalculated from the original data using the proper sign for the anomalous differences, and the new Cα coordinates and structure factors will be deposited.
The authors sincerely regret the confusion that these papers have caused and, in particular, for subsequent research efforts that were unproductive as a result of the original findings.