Biology Reference
In-Depth Information
Fig. 3 The proposed mechanism of the “glutamine switch” (Zhang et al.
2004
). (a) Gln369 forms
two hydrogen bonds (
dotted lines
) with the product 5
0
-AMP in the cAMP-specific PDE4D2
structure. (b) Gln817 of the cGMP-specific PDE5A1 is in an orientation opposite to that of
Gln369 and forms two hydrogen bonds with 5
0
-GMP. (c) and (d) Gln421 in the dual-specific
PDE1B switches its side chain conformation to form two hydrogen bonds with 5
0
-AMP or 5
0
-GMP
invariant Gln817 decreased affinity for cGMP, but did not improve affinity for
cAMP (Zoraghi et al.
2006
). These combined results suggest that the invariant
glutamine in PDEs is important for the substrate binding, but that the orientation of
its side chain may not be a key factor for the differentiation of cAMP and cGMP.
