Conformational changes of the β7–β8 hairpin. (a) Overall structure of the triclinic form of PylRS(c270) (PDB entry 3vqx
, molecule A). Residues 377–386 in the β7–β8 hairpin are coloured red. (b) A close-up stereoview of the β7–β8 hairpin (boxed region in a). The superpositioned Cα traces of the AMP-bound (red and cyan traces, molecules A and B) and BocLys-AMP-bound forms (yellow and orange traces, molecules C and D) with those of the ligand-free (dark blue trace; PDB entry 2e3c
) and two AMPPNP-bound forms (green and pink traces; PDB entries 2zcd
) are shown. The β7–β8 hairpins (residues 374–390) are coloured. (c) Superposition of the present AMP-bound (and BocLys-AMP-bound) form with the PylRS(c270) structures. Tyr384 in each of the PylRS(c270) forms is shown as a ball-and-stick model. The distances between the main-chain Cα atoms of Tyr residue 384 in molecules A (red), C (yellow) and D (orange) of the present triclinic form and that of the AMPPNP-bound form (pink) are as long as 2.3, 11 and 9.3 Å, respectively.