Cell Biology Poster Session

Re: poster 152

On Fri Dec 4, grover wrote
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>Dr. Yunes: Hope you are enjoying the meeting. Great poster.How large are the pores formed due to streptolysin? My understanding was that these were very small pores (compared to those formed with digitonin etc.) and would not allow macromolecules to move across?
>
First of all, thanks for your interesting question. Probably the pores made by streptolysin-O are smaller than those made by digitonin. However, they are big enough to allow large macromolecules (even antibodies) to pass through the cell membrane. I would like to add just a few cites in order to improve my explanation:

a)
Med Microbiol Immunol (Berl) 1993 Sep;182(4):167-75 A guide to the use of pore-forming toxins for controlled permeabilization of cell membranes. Bhakdi S, Weller U, Walev I, Martin E, Jonas D, Palmer M

Depending on the size of the pores one wishes to produce in plasma membranes, the choice will probably fall on one of the three toxins ... S. aureus alpha-toxin should be tried first when pores of 1-1.5 nm diameter are required. This is generally the case when Ca2+ and nucleotide dependence of a given process is being studied. If alpha-toxin does not work, this is probably due to the fact that the toxin either does not produce pores, or that the pores are too small. In this case, high concentrations of alpha-toxin should be tried. If this still does not work, we recommend the use of HlyA. When very large pores are to be created, e.g. for introduction of antibodies into the cells, SLO or another member of this toxin family are the agents of choice.

b)
Infect Immun 1985 Jan;47(1):52-60 Mechanism of membrane damage by streptolysin-O. Bhakdi S, Tranum-Jensen J, Sziegoleit A

Streptolysin-O (SLO) is a thiol-activated, membrane-damaging protein toxin of Mr 69,000 that is produced by most strains of beta-hemolytic group A streptococci. Native, primarily water-soluble toxin molecules bind to cholesterol-containing target membranes to assemble into supramolecular curved rod structures (25 to 100 nm long by ca. 7.5 nm wide), forming rings and arcs that penetrate into the apolar domain of the bilayer ... The embedment of the rings and arcs generates large transmembrane slits or pores of up to 30-nm diameter that can be directly visualized by negative staining and freeze-fracture electron microscopy.

d)
Eur J Biochem 1995 Jul 15;231(2):388-95 Kinetics of streptolysin O self-assembly. Palmer M, Valeva A, Kehoe M, Bhakdi S

Streptolysin O is a member of a family of membrane-damaging toxins that bind to cell membranes containing cholesterol and then polymerize to form large pores. ... by a two-step reaction mechanism: two membrane-bound monomers first associate into a start complex, which then is rapidly extended by the sequential addition of further monomers up to the final oligomer size.

Again, thanks a lot for your interest in our poster. R. Yunes

Mon Dec 7