Abstract:
:The molecular cascade that controls switching of the direction of rotation of Escherichia coli flagellar motors is well known, but the conformational changes that allow the rotor to switch are still unclear. The signaling molecule CheY, when phosphorylated, binds to the C-ring at the base of the rotor, raising the probability that the motor spins clockwise. When the concentration of CheY-P is so low that the motor rotates exclusively counterclockwise (CCW), the C-ring recruits more monomers of FliM and tetramers of FliN, the proteins to which CheY-P binds, thus increasing the motor's sensitivity to CheY-P and allowing it to switch once again. Motors that rotate exclusively CCW have more FliM and FliN subunits in their C-rings than motors that rotate exclusively clockwise. How are the new subunits accommodated? Does the diameter of the C-ring increase, or do FliM and FliN get packed in a different pattern, keeping the overall diameter of the C-ring constant? Here, by measuring fluorescence anisotropy of yellow fluorescent protein-labeled motors, we show that the CCW C-rings accommodate more FliM monomers without changing the spacing between them, and more FliN monomers at the same time as increasing their effective spacing and/or changing their orientation within the tetrameric structure.
journal_name
Biophys Jjournal_title
Biophysical journalauthors
Hosu BG,Berg HCdoi
10.1016/j.bpj.2017.12.001subject
Has Abstractpub_date
2018-02-06 00:00:00pages
641-649issue
3eissn
0006-3495issn
1542-0086pii
S0006-3495(17)35048-8journal_volume
114pub_type
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