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Figure 4.
View larger version (77K): [in
this window] [in
a new window] Fig. 4. Schematic representation of the
decoding pathway. (A) The L7/L12 stalk recruits TC to a ribosome
with deacylated tRNA in the E site and peptidyl-tRNA in the P
site. The black frame represents the enlarged area depicted in
(B) to (E). (B) The tRNA samples codon-to-anticodon pairing
until a match (C) is sensed, by decoding center nucleotides 530,
1492, and 1493 (1). Codon recognition triggers domain closure of
the 30S subunit (2), bringing the shoulder domain into contact
with EF-Tu and shifting the β loop at 230 to 237 of domain 2
(3). This changes the conformation of the acceptor end of the
tRNA (4), disrupting its contacts with switch I, which becomes
disordered (5), opening the hydrophobic gate to allow His^84 to
catalyze GTP hydrolysis. (D) GTP hydrolysis and P[i] release
cause domain rearrangement of EF-Tu, leading to its release from
the ribosome and (E and F) accommodation of aminoacyl-tRNA.
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