Premium
A pH‐dependent Switch Regulates Chaperone Activity
Author(s) -
Rajagopal Ponni,
Jehle Stefan,
Dove Katja,
Pierini Chris,
Delbecq Scott,
Klevit Rachel E
Publication year - 2011
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.25.1_supplement.907.4
Subject(s) - oligomer , chaperone (clinical) , chemistry , biophysics , protein subunit , small angle x ray scattering , biochemistry , microbiology and biotechnology , biology , medicine , pathology , physics , organic chemistry , gene , scattering , optics
Hypoxic conditions often found in cancerous and ischemic cells induce the over‐expression of a non‐ATP dependent stress chaperone, αB‐Crystallin (αB). Investigation of αB's response to hypoxia can help develop therapeutic strategies to combat disease. αB is a polydisperse oligomer, ~ 580 kDa in size and composed of ~28 subunits. We have used solution‐state and solid‐state NMR, SAXS, EM data, and computational methodologies to determine a structural model of the oligomer. NMR data show that there is an increased exposure of substrate binding sites in αB at lower pH (acidification is a consequence of hypoxia) presumably to confer protection to proteins and enhance cellular survival. αB has a conserved α‐crystallin domain flanked by variable N‐ and C‐ terminal regions. The α‐crystallin domain forms a homodimeric (20 kDa) building block of the oligomer and the inter‐subunit interactions of the N‐ and C‐termini leads to higher order oligomers. The truncated α‐crystallin domain has proved to be a good functional mimic of the oligomer and we are using the domain to identify the basis of the pH‐dependent behavior. We have identified critical residues that are responsible for the sharp pH‐dependent switch by determining pKa values and using mutational analysis. Mutations that abrogate this pH‐dependent switch have an adverse effect on the chaperone activity of αB. Funding from NIH‐1R01EY017370 is acknowledged.