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Figure 1.
Figure 1. DAPP1-PH and Grp1-PH Recognize Distinct Patterns
of Phosphate Groups(A) Binding of Ins(1,3,4)P[3] (magenta,
squares), and Ins(1,5,6)P[3] (which has the same phosphate
arrangement as Ins(3,4,5)P[3]) (cyan, triangles) to DAPP1-PH
(left) and Grp1-PH (right) is compared using a
^3H-Ins(1,3,4,5)P[4] competition assay ([17]). DAPP1-PH binds
10-fold more strongly to Ins(1,3,4)P[3] than to the
Ins(3,4,5)P[3] analog, while the converse is true for
Grp1-PH.(B) Structures of the inositol trisphosphates.
Ins(1,3,4)P[3] (magenta) and Ins(3,4,5)P[3] (cyan) are
compared. Note that Ins(3,4,5)P[3] is equivalent to
Ins(1,5,6)P[3] except in the positioning of the single axial
hydroxyl group (2-OH). Ins(3,4,5)P[3] is not commercially
available, so Ins(1,5,6)P[3] was used for the experiment shown
in (A). Since Ins(3,5,6)P[3] and Ins(1,3,4)P[3] bind identically
to DAPP1-PH (Table 1), we suggest that the axial 2-hydroxyl is
not likely to be important in defining binding specificity.
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