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Figure 6.
Bem1p PX domain in the absence and presence of PS and
PtdIns(4)P.A, C, and E show the electrostatic potential mapped
to the membrane-binding surface of the PX domain. B, D, and F
represent the PX domain as a C-α backbone and the electrostatic
potential as a two-dimensional contour. The molecules are
rotated 90° forward from A, C, and E, and the
membrane-binding surfaces point downward in this orientation.
Even in the absence of lipids (A and B), Tyr^360 is exposed over
the electrostatic potential surface, accounting for the high
intrinsic membrane penetrating activity of Bem1p-PX. Upon
binding to PS (C and D), the electrostatic potential of the
membrane-binding surface of Bem1p-PX is relatively unchanged.
Upon binding to PtdIns(4)P (E and F), the positive electrostatic
potential of the membrane-binding surface of Bem1p-PX is greatly
decreased, exposing Trp^346, which will further penetrate into
the membrane. PtdIns(4)P is colored yellow, and Trp^346 and
Tyr^360 are colored green. PS is not shown.
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