Ton

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The Ton System
The Ton System[1]

Contents

Structure

The Ton system comprises of the triumvirate TonB/ExbB/ExbD inner membrane complex.

Function

The Ton proteins are involved in the uptake of vitamin B12 and chelated-iron into the cell[2], and the system as a whole is known to be an energy-transducing system. Each of the three proteins involved have their separate role[3]. For more information, see the respective pages for TonB, ExbB and ExbD.

The Ton system can be exploited by group B Colicins {see Colicin for more details) which include[4][5]:

It is interesting to note that the name 'Ton' comes its resistance to the T1 phage[5].

Interaction of Ton proteins

Like in the Tol complex, the Ton system proteins interact with each other[6]:

  1. the transmembrane domain of TonB interacts with both ExbB and ExbD, which contribute to the stability of the protein and support the TonB-dependent active transport across the outer membrane.
  2. ExbB and ExbD interact with each other, which has been suggested to play a part in the mechanism of energy transduction

3D structures of TonB

TonB

References

  1. Witty M, Sanz C, Shah A, Grossmann JG, Mizuguchi K, Perham RN, Luisi B. Structure of the periplasmic domain of Pseudomonas aeruginosa TolA: evidence for an evolutionary relationship with the TonB transporter protein. EMBO J. 2002 Aug 15;21(16):4207-18. PMID:12169623
  2. Cascales E, Buchanan SK, Duche D, Kleanthous C, Lloubes R, Postle K, Riley M, Slatin S, Cavard D. Colicin biology. Microbiol Mol Biol Rev. 2007 Mar;71(1):158-229. PMID:17347522 doi:10.1128/MMBR.00036-06
  3. Held KG, Postle K. ExbB and ExbD do not function independently in TonB-dependent energy transduction. J Bacteriol. 2002 Sep;184(18):5170-3. PMID:12193634
  4. Cascales E, Buchanan SK, Duche D, Kleanthous C, Lloubes R, Postle K, Riley M, Slatin S, Cavard D. Colicin biology. Microbiol Mol Biol Rev. 2007 Mar;71(1):158-229. PMID:17347522 doi:10.1128/MMBR.00036-06
  5. 5.0 5.1 Davies JK, Reeves P. Genetics of resistance to colicins in Escherichia coli K-12: cross-resistance among colicins of group B. J Bacteriol. 1975 Jul;123(1):96-101. PMID:124727
  6. Higgs PI, Myers PS, Postle K. Interactions in the TonB-dependent energy transduction complex: ExbB and ExbD form homomultimers. J Bacteriol. 1998 Nov;180(22):6031-8. PMID:9811664

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