Human βB2-Crystallin Forms a Face-en-Face Dimer in Solution: An Integrated NMR and SAXS Study

Structure. 2017 Mar 7;25(3):496-505. doi: 10.1016/j.str.2017.02.001. Epub 2017 Feb 23.


βγ-Crystallins are long-lived eye lens proteins that are crucial for lens transparency and refractive power. Each βγ-crystallin comprises two homologous domains, which are connected by a short linker. γ-Crystallins are monomeric, while β-crystallins crystallize as dimers and multimers. In the crystal, human βB2-crystallin is a domain-swapped dimer while the N-terminally truncated βB1-crystallin forms a face-en-face dimer. Combining and integrating data from multi-angle light scattering, nuclear magnetic resonance, and small-angle X-ray scattering of full-length and terminally truncated human βB2-crystallin in solution, we show that both these βB2-crystallin proteins are dimeric, possess C2 symmetry, and are more compact than domain-swapped dimers. Importantly, no inter-molecular paramagnetic relaxation enhancement effects compatible with domain swapping were detected. Our collective experimental results unambiguously demonstrate that, in solution, human βB2-crystallin is not domain swapped and exhibits a face-en-face dimer structure similar to the crystal structure of truncated βB1-crystallin.

Keywords: MALS; NMR; PRE; SAXS; cataract; domain swapping; eye lens; integrated structural biology; spin label; βB2-crystallin.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Crystallography, X-Ray
  • Humans
  • Models, Molecular
  • Protein Multimerization
  • Protein Structure, Quaternary
  • Scattering, Small Angle
  • Sequence Deletion
  • X-Ray Diffraction
  • beta-Crystallin B Chain / chemistry*
  • beta-Crystallin B Chain / genetics*


  • beta-Crystallin B Chain
  • beta-crystallin B2