Molecular Weight of the Photoprotein Aequorin.

摘要

Aequorin was studied by means of sedimentation analysis, gel filtration, gel electrophoresis, and functional group analysis. Except for gel filtration through Sephadex G-100 and sodium dodecyl sulfate gel electrophoresis, which indicated molecular weights between 15,000 and 23,000, the data from all other methods indicated a molecular weight of 31,000 plus or minus 1000, and a one to one ratio of functional groups to aequorin molecules, with no evidence of subunits. Aggregation of the native protein, however, was shown to occur at rates which, though negligible at pH 9, become significant and faster as the pH is lowered, especially below pH 6.5. The rate was also faster at 20 degrees than at 7 degrees. Reversal of aggregation occurred at pH 9.0-9.5. After aequorin had been denatured by heat, sodium dodecyl sulfate, or urea, or after it had undergone the light-emitting reaction triggered by Ca(2+) yielding the blue fluorescent substance 'BFP,' the protein product in each case showed a tendency to dimerize. The dimerization as well as aggregation could be inhibited or reversed by p-benzoquinone. (Author)