Dm. Czajkowsky et al., STAPHYLOCOCCAL ALPHA-HEMOLYSIN CAN FORM HEXAMERS IN PHOSPHOLIPID-BILAYERS, Journal of Molecular Biology, 276(2), 1998, pp. 325-330
Atomic force microscopy (AFM) was used to study the structure of the s
taphylococcal alpha-hemolysin (alpha HL) oligomer formed in supported
phospholipid bilayers. In contrast to the recent X-ray crystallographi
c demonstration of a heptameric stoichiometry for the oligomer formed
in deoxycholate (DOC) micelles, the high-resolution unprocessed AFM im
ages unequivocally revealed a hexamer in these phospholipid bilayers.
Independent support of this hexameric stoichiometry was obtained from
the measurements of the lattice constant in the AFM images and from ge
l electrophoresis. Therefore, alpha HL can form two different, energet
ically stable oligomers, which differ in at least stoichiometry but pe
rhaps subunit structure as well. Furthermore, stable, incomplete oligo
mers were observed in the AFM images, which may be of relevance to the
mechanism by which alpha HL damages the cell. (C) 1998 Academic Press
Limited.