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Figure 4.
Figure 4. Comparison of the G3 Regions in psToc34 and Ras p21
(A) The conformation of G3/switch II is identical in the
GMPPNP- and the GDP-bound states of psToc34. Gly96 is in
hydrogen-bonding distance to the γ-phosphate, and is conserved
in the GTPase G3 motif (DxxG). Leu97, directly following the G3
motif, enters a hydrophobic pocket between helices α2 and α3.
(B) A similar representation as in (A) for G3/switch II of
Ras p21 (PDB code: 5P21) (Pai et al., 1990). Gly60 is in
hydrogen-bonding distance to the γ-phosphate in the
GMPPNP-bound state; different from psToc34, Gly60 is turned away
from the binding pocket in the GDP-bound state of Ras p21 (not
shown). The equivalent residue to Leu97 of psToc34 is the
catalytic residue Gln61 in Ras p21, which is turned toward the
nucleotide.
(C) The alignment shows the G3 region of six
members of the Aig1/Toc34/Toc159-like paraseptin GTPase family,
together with three GTPases of the TRAFAC class.
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