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Figure 3.
Figure 3. Conformational changes in the L16 loop and disruption
of a salt-bridge are fingerprints of the active p38α
molecules. (a) The conformational changes within the L16 loops
of p38α^D176A + F327L (blue) and p38α^D176A + F327S (yellow)
in reference to p38α^D176A (magenta) and p38α^wt (gray).
Mutations of Phe327 to serine or leucine results in a
conformational change in the L16 loop. Residues 327 in the
mutants' structures subsequently adopt a different conformation.
However, the conformation of Trp337 and Tyr69 remains highly
similar in all structures. (b) Segments of L16 loop from
p38α^D176A (left), p38α^D176A + F327L (center) and p38α^D176A
+ F327S (right) are superimposed with p38α^wt as a reference.
The conformation of the L16 loop in the structure of p38α^D176A
is almost identical (except minor changes in Asp331) to that of
p38α^wt. Mutation of Phe327 leads to the unwinding and a shift
of the main-chain helical conformation in the L16, and
subsequently the side-chains of residues 324 to 330 adopt a
different position in both p38α^D176A + F327L and p38α^D176A +
F327S models (center and right). (c) A salt bridge interaction
is formed between the negatively charged carboxyl group of
Glu328 and the positively charged guanidine of Arg70 (green
broken lines) in both p38α^wt and p38α^D176A (left). This salt
bridge is disrupted in the structures of p38α^D176A + F327L
and p38α^D176A + F327S (center and right, respectively) due to
the conformational change in the L16 loop. In this regard, the
unpaired Arg70 acquire new conformations; in p38α^D176A + F327L
Arg70 adopts a dual conformation whereas in p38α^D176A + F327S
only one. The C^α atom of Glu328 is shifted 2.53 Å and
1.11 Å in the structures of p38α^D176A + F327L and
p38α^D176A + F327S, respectively, relative to the p38α^wt
structure. The orientation of the side-chains is somewhat
different as Lys66 is stabilizing the carbonyl oxygen of Glu328
by forming an H-bond interaction in p38α^D176A + F327S similar
to p38α^wt but not in p38α^D176A + F327L (yellow broken
lines). Figure 3. Conformational changes in the L16 loop and
disruption of a salt-bridge are fingerprints of the active p38α
molecules. (a) The conformational changes within the L16 loops
of p38α^D176A + F327L (blue) and p38α^D176A + F327S (yellow)
in reference to p38α^D176A (magenta) and p38α^wt (gray).
Mutations of Phe327 to serine or leucine results in a
conformational change in the L16 loop. Residues 327 in the
mutants' structures subsequently adopt a different conformation.
However, the conformation of Trp337 and Tyr69 remains highly
similar in all structures. (b) Segments of L16 loop from
p38α^D176A (left), p38α^D176A + F327L (center) and p38α^D176A
+ F327S (right) are superimposed with p38α^wt as a reference.
The conformation of the L16 loop in the structure of p38α^D176A
is almost identical (except minor changes in Asp331) to that of
p38α^wt. Mutation of Phe327 leads to the unwinding and a shift
of the main-chain helical conformation in the L16, and
subsequently the side-chains of residues 324 to 330 adopt a
different position in both p38α^D176A + F327L and p38α^D176A +
F327S models (center and right). (c) A salt bridge interaction
is formed between the negatively charged carboxyl group of
Glu328 and the positively charged guanidine of Arg70 (green
broken lines) in both p38α^wt and p38α^D176A (left). This salt
bridge is disrupted in the structures of p38α^D176A + F327L and
p38α^D176A + F327S (center and right, respectively) due to the
conformational change in the L16 loop. In this regard, the
unpaired Arg70 acquire new conformations; in p38α^D176A + F327L
Arg70 adopts a dual conformation whereas in p38α^D176A + F327S
only one. The C^α atom of Glu328 is shifted 2.53 Å and
1.11 Å in the structures of p38α^D176A + F327L and
p38α^D176A + F327S, respectively, relative to the p38α^wt
structure. The orientation of the side-chains is somewhat
different as Lys66 is stabilizing the carbonyl oxygen of Glu328
by forming an H-bond interaction in p38α^D176A + F327S similar
to p38α^wt but not in p38α^D176A + F327L (yellow broken
lines).
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