Biochemistry I   Spring & Fall Terms

Hemolysin Structure

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  Distances (Å):
  Membrane thickness.
  Channel diameter.
  Channel constriction at Lys 147 and Met 113 or Glu 111).
      (Fall Term '00, PS#9, question 7)

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a-Hemolysin from Staphylococcus aureus
Hemolysins* are bacterial toxins that function by assembling identical subunits into a membrane-spanning pore. Cell lysis (and death) is caused by the leakage of small molecules and ions through the large water-filled central channel. The initial view of the heptamer is in the plane of the membrane with each subunit in a different color. The overall shape resembles a mushroom with the stem penetrating the membrane bilayer and the cap extending into the extracellular space. Each subunit has 16 antiparallel b-strands and four short a-helices. (Fig. 2a & b).

*The structure of a-Hemolysin from Staphylococcus aureus is described by Song et al. (1996) Science 274 1859-1865. The coordinate file is 7ahl.pdb (from which the waters were removed). (References to Figs. above are to those of Song et al.)

Four more membrane protein structures:
 Bacteriorhodopsin       K+-Channel       Maltoporin       a-Hemolysin       Reaction Center

Back to the Protein Structure List.

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8.21.04