Scam Feels the Pinch

The paper by Movileanu et al. 2001 in this issue of The Journal describes a test of the applicability of the substituted-cysteine-accessibility method (SCAM; Akabas et al. 1992; Akabas et al. 1994) to the problem of locating the narrowest region of a channel lumen. Movileanu et al. 2001 use unusually large sulfhydryl-directed reagents to probe the wide bore channel formed by Staphylococcal α-hemolysin. The structure of the membrane-associated form of this protein has been solved to high resolution (Song et al. 1996). It is a mushroom-shaped heptameric complex that inserts in the membrane of a susceptible cell with the wide cap on the extracellular side, or on the cis side of an artificial planar lipid membrane, and with the stem traversing the bilayer (see Figure 1 in Movileanu et al. 2001). The entrance to...