Conformation of concanavalin A and its fragments in aqueous solution and organic solvent-water mixtures.
The conformations of concanavalin A (con A), an all-beta protein, and its three CNBr-cleaved fragments were studied by CD. Con A in buffer showed a 197 nm maximum and a 223 nm minimum, which were red-shifted by 6-7 nm from those of regular all-beta proteins and beta-sheet of (Lys)n. Fragment 1 (residue 1-42) resembled an unordered form with a CD maximum at 200 nm, but fragments 2 (residues 43-129) and 3 (residues 130-237) showed a regular CD spectrum with two extrema at 192-193 nm (+) and 214-216 nm (-). Equimolar mixture of the three fragments showed some degree of interaction, but did not reconstitute the conformation of native con A, probably because of the loss of bound Ca2+ and Mn2+ ions in the fragments. In ethanol-, methanol-, and dioxane-water mixed solvents, con A and its fragments remained as beta-sheet. In contrast, addition of trifluoroethanol and sodium dodecyl sulfate induced alpha-helix at the expense of beta-sheet for con A and its fragments in aqueous solution. In 80% trifluoroethanol, the induced helicities exceeded their sequence-predicted helix-potentials, but in 10 mM sodium dodecyl sulfate the helicities agreed well with corresponding predictions.
Wang
J M
JM
Cardiovascular Research Institute, University of California, San Francisco.
Takeda
A
A
Yang
J T
JT
Wu
C S
CS
D002021:Buffers; D002942:Circular Dichroism; D003208:Concanavalin A / Q000737:chemistry*; D004146:Dioxanes; D000431:Ethanol; D000432:Methanol; D011487:Protein Conformation; D012967:Sodium Dodecyl Sulfate; D012997:Solvents; D014270:Trifluoroethanol; D014867:Water; D014961:X-Ray Diffraction
D002021:Buffers; D004146:Dioxanes; D012997:Solvents; D014867:Water; D003208:Concanavalin A; D012967:Sodium Dodecyl Sulfate; D000431:Ethanol; D014270:Trifluoroethanol; C025223:1,4-dioxane; D000432:Methanol