Details

Autor(en) / Beteiligte

• Bharat, Somireddy Venkata
• Shekhtman, Alexander
• Pande, Jayanti

Titel

The cataract-associated V41M mutant of human γS-crystallin shows specific structural changes that directly enhance local surface hydrophobicity

Ist Teil von

• Biochemical and biophysical research communications, 2014-01, Vol.443 (1), p.110-114

Ort / Verlag

United States: Elsevier Inc

Erscheinungsjahr

2014

Quelle

MEDLINE

Beschreibungen/Notizen

• •We present NMR analysis of V41M, a cataract-causing mutant of human γS-crystallin.•Mutation alters strand–strand interactions throughout the N-terminal domain.•Mutation directly affects Trp46 due to key Met41-S–Trp46-pi interactions.•We identify the basis of the surface hydrophobicity increase and residues involved. The major crystallins expressed in the human lens are γS-, γC- and γD-crystallins. Several mutations in γS-crystallin are associated with hereditary cataracts, one of which involves the substitution of a highly conserved Valine at position 41 to Methionine. According to a recent report, the mutant protein, V41M, shows lower stability and increased surface hydrophobicity compared to the wild-type, and a propensity for self-aggregation. Here we address the structural differences between the two proteins, with residue-level specificity using NMR spectroscopy. Based on the structural model of the mutant protein, our results clearly show that the mutation creates a major local perturbation almost at the junction of the first and second “Greek-key” motifs in the N-terminal domain. A larger section of the second motif (residues 44–86) appears to be mainly affected. Based on the sizeable chemical shift of the imino proton of the indole side-chain of Trp46 in V41M, we suggest that the sulphur atom of Met41 is involved in an S–π interaction with Trp46. This interaction would bring the last β-strand of the first “Greek-key” motif closer to the first β-strand of the second motif. This appears to lead to a domino effect, towards both the N- and C-terminal ends, even as it decays off substantially beyond the domain interface. During this process discreet hydrophobic surface patches are created, as revealed by ANS-binding. Such changes would not affect the secondary structure or cause a major change in the tertiary structure, but can lead to self-aggregation or aberrant binding interactions of the mutant protein in vivo, and lead to lens opacity or cataract.