2HP7

Structure of FliM provides insight into assembly of the switch complex in the bacterial flagella motor

Summary for 2HP7

• Entry DOI: 10.2210/pdb2hp7/pdb
• Descriptor: Flagellar motor switch protein FliM (2 entities in total)
• Functional Keywords: bacterial chemotaxis, flagellar switch complex, signaling protein
• Biological source: Thermotoga maritima
• Total number of polymer chains: 1
• Total formula weight: 21044.14

Authors

Crane, B.R.,Park, S.,Lowder, B.,Bilwes, A.M.,Blair, D.F. (deposition date: 2006-07-17, release date: 2006-08-08, Last modification date: 2024-02-14)

Primary citation

Park, S.,Lowder, B.,Bilwes, A.M.,Blair, D.F.,Crane, B.R.
Structure of FliM provides insight into assembly of the switch complex in the bacterial flagella motor.
Proc.Natl.Acad.Sci.Usa, 103:11886-11891, 2006

PubMed Abstract: Bacteria switch the direction their flagella rotate to control movement. FliM, along with FliN and FliG, compose a complex in the motor that, upon binding phosphorylated CheY, reverses the sense of flagellar rotation. The 2.0-A resolution structure of the FliM middle domain (FliM(M)) from Thermotoga maritima reveals a pseudo-2-fold symmetric topology similar to the CheY phosphatases CheC and CheX. A variable structural element, which, in CheC, mediates binding to CheD (alpha2') and, in CheX, mediates dimerization (beta'(x)), has a truncated structure unique to FliM (alpha2'). An exposed helix of FliM(M) (alpha1) does not contain the catalytic residues of CheC and CheX but does include positions conserved in FliM sequences. Cross-linking experiments with site-directed cysteine mutants show that FliM self-associates through residues on alpha1 and alpha2'. CheY activated by BeF(3)(-) binds to FliM with approximately 40-fold higher affinity than CheY (K(d) = 0.04 microM vs. 2 microM). Mapping residue conservation, suppressor mutation sites, binding data, and deletion analysis onto the FliM(M) surface defines regions important for contacts with the stator-interacting protein FliG and for either counterclockwise or clockwise rotation. Association of 33-35 FliM subunits would generate a 44- to 45-nm-diameter disk, consistent with the known dimensions of the C-ring. The localization of counterclockwise- and clockwise-biasing mutations to distinct surfaces suggests that the binding of phosphorylated CheY cooperatively realigns FliM around the ring.

PubMed: 16882724
DOI: 10.1073/pnas.0602811103

Experimental method

X-RAY DIFFRACTION (2 Å)