Crystal Structure of Chicken ?S-Crystallin Reveals Lattice Contacts with Implications for Function in the Lens and the Evolution of the ??-Crystallins.

ABSTRACT: Previous attempts to crystallize mammalian ?S-crystallin were unsuccessful. Native L16 chicken ?S crystallized avidly while the Q16 mutant did not. The X-ray structure for chicken ?S at 2.3 Å resolution shows the canonical structure of the superfamily plus a well-ordered N arm aligned with a ? sheet of a neighboring N domain. L16 is also in a lattice contact, partially shielded from solvent. Unexpectedly, the major lattice contact matches a conserved interface (QR) in the multimeric ?-crystallins. QR shows little conservation of residue contacts, except for one between symmetry-related tyrosines, but molecular dipoles for the proteins with QR show striking similarities while other ?-crystallins differ. In ?S, QR has few hydrophobic contacts and features a thin layer of tightly bound water. The free energy of QR is slightly repulsive and analytical ultracentrifugation confirms no dimerization in solution. The lattice contacts suggest how ?-crystallins allow close packing without aggregation in the crowded environment of the lens.

SUBMITTER: Sagar V 

PROVIDER: S-EPMC5518705 | biostudies-literature | 2017 Jul

REPOSITORIES: biostudies-literature