Characterisation of the heptameric pore-forming complex of the Aeromonas toxin aerolysin using MALDI-TOF mass spectrometry.
Aerolysin, a virulence factor secreted by Aeromonas hydrophila, is representative of a group of beta-sheet toxins that must form stable homooligomers in order to be able to insert into biological membranes and generate channels. Electron microscopy and image analysis of two-dimensional membrane crystals had previously revealed a structure with 7-fold symmetry suggesting that aerolysin forms heptameric oligomers [Wilmsen et al. (1992) EMBO J. 11, 2457-2463]. However, this unusual molecularity of the channel remained to be confirmed by an independent method since low-resolution electron crystallography had led to artefactual data for other pore-forming toxins. In this study, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) was used to measure the mass of the aerolysin oligomer preparation. A mass of 333 850 Da was measured, fitting very well with a heptameric complex (expected mass: 332 300 Da). These results confirm the earlier evidence that the aerolysin oligomer is a heptamer and also show that MALDI-TOF mass spectrometry could be a valuable tool to study non-covalent association of proteins.
Moniatte
M
M
Laboratoire de Spectrometrie de Masse Bio-Organique associe au CNRS, Universite Louis Pasteur, Strasbourg, France.
van der Goot
F G
FG
Buckley
J T
JT
Pattus
F
F
van Dorsselaer
A
A
D016980:Aeromonas hydrophila / Q000737:chemistry*; D001427:Bacterial Toxins / Q000737:chemistry*; D004792:Enzyme Precursors / Q000737:chemistry; D007834:Lasers; D013058:Mass Spectrometry / Q000379:methods*; D008970:Molecular Weight; D052899:Pore Forming Cytotoxic Proteins; D011487:Protein Conformation
D001427:Bacterial Toxins; D004792:Enzyme Precursors; D052899:Pore Forming Cytotoxic Proteins; C032676:aerolysin