Structural insights into the membrane-extracted dimeric form of the ATPase TraB from the Escherichia coli pKM101 conjugation system.
BACKGROUND
Type IV secretion (T4S) systems are involved in secretion of virulence factors such as toxins or transforming molecules, or bacterial conjugation. T4S systems are composed of 12 proteins named VirB1-B11 and VirD4. Among them, three ATPases are involved in the assembly of the T4S system and/or provide energy for substrate transfer, VirB4, VirB11 and VirD4. The X-ray crystal structures of VirB11 and VirD4 have already been solved but VirB4 has proven to be reluctant to any structural investigation so far.


RESULTS
Here, we have used small-angle X-ray scattering to obtain the first structural models for the membrane-extracted, dimeric form of the TraB protein, the VirB4 homolog encoded by the E. coli pKM101 plasmid, and for the monomeric soluble form of the LvhB4 protein, the VirB4 homolog of the T4S system encoded by the Legionella pneumophila lvh operon. We have obtained the low resolution structures of the full-length TraB and of its N- and C-terminal halves. From these SAXS models, we derive the internal organisation of TraB. We also show that the two TraB N- and C-terminal domains are independently involved in the dimerisation of the full-length protein.


CONCLUSIONS
These models provide the first structural insights into the architecture of VirB4 proteins. In particular, our results highlight the modular arrangement and functional relevance of the dimeric-membrane-bound form of TraB.
Institute of Structural and Molecular Biology, UCL/Birkbeck, Malet Street, London WC1E 7HX, UK.
Eric
E
Durand
Gabriel
G
Waksman
Veronique
V
Receveur-Brechot
D000251:Adenosine Triphosphatases / Q000235:genetics / Q000378:metabolism; D001425:Bacterial Outer Membrane Proteins / Q000737:chemistry* / Q000648:ultrastructure; D001426:Bacterial Proteins / Q000737:chemistry* / Q000648:ultrastructure; D002462:Cell Membrane / Q000648:ultrastructure*; D003227:Conjugation, Genetic; D018360:Crystallography, X-Ray; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D010957:Plasmids / Q000235:genetics; D011487:Protein Conformation; D055503:Protein Multimerization; D053838:Scattering, Small Angle; D037521:Virulence Factors / Q000235:genetics; D014961:X-Ray Diffraction / Q000379:methods
D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; C459580:Lvh protein, Legionella pneumophila; D037521:Virulence Factors; C082576:traB protein, Bacteria; D000251:Adenosine Triphosphatases
J Bacteriol. 2010 May;192(9):2315-23
20172994
J Bacteriol. 2008 Aug;190(15):5472-9
18539740
Mol Microbiol. 1999 Jun;32(6):1239-53
10383764
J Appl Crystallogr. 2009 Apr 1;42(Pt 2):342-346
27630371
Biophys J. 1986 Dec;50(6):1035-42
3801566
J Biol Chem. 2004 Dec 31;279(53):55985-94
15502162
Cell. 2010 Jan 8;140(1):162-162.e1
20085708
Mol Cell. 2000 Dec;6(6):1461-72
11163218
J Bacteriol. 2003 Feb;185(3):1045-58
12533481
J Biol Chem. 1991 Dec 25;266(36):24420-7
1837021
EMBO J. 2008 Sep 3;27(17):2271-80
18668121
Nat Rev Microbiol. 2003 Nov;1(2):137-49
15035043
FEMS Microbiol Rev. 2006 Nov;30(6):942-66
17026718
Biochem J. 2010 Jan 15;425(3):475-88
20070257
Mol Microbiol. 2002 Mar;43(5):1359-65
11918819
Curr Opin Microbiol. 2003 Feb;6(1):29-34
12615216
Nature. 2009 Dec 24;462(7276):1011-5
19946264
Science. 2009 Jan 9;323(5911):266-8
19131631
J Cell Biol. 2002 Aug 5;158(3):415-9
12147677
Proc Natl Acad Sci U S A. 2005 Feb 1;102(5):1685-90
15668378
Nat Rev Microbiol. 2009 Oct;7(10):703-14
19756009
Science. 1999 May 21;284(5418):1328-33
10334982
Nat Rev Microbiol. 2007 Nov;5(11):839-51
17938627
Biophys J. 2001 Jun;80(6):2946-53
11371467
Plant J. 2000 Jul;23(1):11-28
10929098
Vet Microbiol. 2002 Dec 20;90(1-4):341-8
12414154