Surface properties of membrane systems. Transport of staphylococcal delta-toxin from aqueous to membrane phase.
Hemolytic delta-toxin from Staphylococcus aureus was soluble in either water, methanol or chloroform/methanol (2 : 1, v/v). The toxin spread readily from distilled water into films with pressures (pi) of 10 dynes/cm on water and 30 dynes/cm on 6 M urea; from chloroform/methanol it produced 40 dynes/cm pressure on distilled water. The toxin adsorbed barely from water (pi = 1 dyne/ cm) but it did rapidly from 6 M urea (pi = 35 dynes/cm). The protein films had unusually high surface potentials, which increased with the film pressure and decreased with increasing both pH and urea concentration in the aqueous phase. The fluorescence of 1-aniline 8-naphthalene sulfonate with delta-toxin was much greater than that with RNAase and dipalmitoyl phosphatidylcholine itself, indicating probably a marked lipid-binding character of the toxin. By circular dichroism the alpha-helix content of delta-toxin was 42% in water, 45% in methanol, 24% in 6 M urea. Infrared spectroscopy showed predominant alpha-helix in both 2H2O and deuterated chloroform/methanol as well as in films spread from either solvent on 2H2O. In spreading from 6 M [2H]urea, in which the major infrared absorption was that of [2H]urea with peaks at 1600 and 1480 cm(-1), the delta-toxin film showed prevalently non-alpha-helix structures with major peak intensities at 1633 cm(-1) > 1680 cm(-1), indicating the appearance of new beta-aggregated and beta-antiparallel pleated sheet structures in the film. The data prove that (1) high pressure protein films can consist of alpha-helix as well as non-alpha-helix structures and, differently from another cytolytic protein, melittin, delta-toxin does not resume the alpha-helix conformation in going into the film phase from the extended chain in 6 M urea; (2) conformational changes are important in the transport of proteins from aqueous to lipid or membrane phase; (3) delta-toxin is by far more versatile in structural dynamics and more surface active than alpha-toxin.
Colacicco
G
G
Department of Pathology, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
Basu
M K
MK
Buckelew
A R
AR
Bernheimer
A W
AW
D015060:1,2-Dipalmitoylphosphatidylcholine / Q000737:chemistry; D000327:Adsorption; D000817:Anilino Naphthalenesulfonates / Q000494:pharmacology; D001427:Bacterial Toxins / Q000737:chemistry* / Q000378:metabolism; D001671:Biochemistry / Q000379:methods; D002462:Cell Membrane / Q000378:metabolism*; D002725:Chloroform / Q000737:chemistry; D002942:Circular Dichroism; D006863:Hydrogen-Ion Concentration; D007477:Ions; D008555:Melitten / Q000737:chemistry; D000432:Methanol / Q000737:chemistry; D008856:Microscopy, Fluorescence; D008970:Molecular Weight; D011312:Pressure; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D012260:Ribonucleases / Q000737:chemistry; D013055:Spectrophotometry, Infrared; D013499:Surface Properties; D013696:Temperature; D013997:Time Factors; D010738:Type C Phospholipases / Q000737:chemistry; D014508:Urea / Q000737:chemistry / Q000494:pharmacology; D014867:Water / Q000737:chemistry
D000817:Anilino Naphthalenesulfonates; D001427:Bacterial Toxins; D007477:Ions; C025971:staphylococcal delta toxin; D014867:Water; D008555:Melitten; D015060:1,2-Dipalmitoylphosphatidylcholine; C027132:1-anilino-8-naphthalenesulfonate; D002725:Chloroform; D014508:Urea; D012260:Ribonucleases; D010738:Type C Phospholipases; D000432:Methanol