The domains in gammaB-crystallin: identical fold-different stabilities.
gammaB-crystallin from vertebrate eye lens is an all beta-sheet two-domain protein with a high degree of intrachain symmetry. Its N and C-terminal domains show high levels of sequence similarity and structural identity. In natural gammaB-crystallin, the domains fold independently. The recombinantly expressed isolated domains are stable monomeric proteins, which do not associate spontaneously to form a gammaB-like dimer. In contrast to their identical folding topology, the two domains obviously follow different folding mechanisms. While the two-state model is valid for the C-terminal domain, the folding behaviour of the N-terminal domain is more complex. The stability of the C-terminal domain is strongly dependent on pH. At pH 2, the C-terminal domain in its isolated form is significantly less stable than within the gammaB-molecule. In contrast, the isolated N-terminal domain does not differ in its stability from the N-terminal domain in wild-type gammaB-crystallin. The strongly decreased stability of the C-terminal domain at acid pH allowed a dissection of the intrinsic stabilities of the domains and their interactions in gammaB-crystallin. At pH 2, domain interactions contribute -16 kJ/mol to the overall stability of gammaB-crystallin.
Mayr
E M
EM
Institut für Biophysik und Physikalische Biochemie, Universität Regensburg, Germany.
Jaenicke
R
R
Glockshuber
R
R
D000595:Amino Acid Sequence; D002942:Circular Dichroism; D003459:Crystallins / Q000737:chemistry* / Q000235:genetics; D019281:Dimerization; D019791:Guanidine; D006146:Guanidines / Q000494:pharmacology; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry* / Q000235:genetics; D011489:Protein Denaturation; D017510:Protein Folding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry; D017386:Sequence Homology, Amino Acid; D013050:Spectrometry, Fluorescence; D013056:Spectrophotometry, Ultraviolet; D014508:Urea / Q000494:pharmacology
D003459:Crystallins; D006146:Guanidines; D010446:Peptide Fragments; D011994:Recombinant Proteins; D014508:Urea; D019791:Guanidine