An electrophoretic method to detect cold-induced dissociation of proteins in crude extracts of higher plants.

The phenomenon of cold denaturation has been firmly established recently in several proteins. Some multimeric enzymes from plant origins are believed to dissociate under some circumstances in the cold. To determine the presence and number of soluble, non-membrane-bound protein that undergoes cold-induced dissociation in plants, we have devised a special two-dimensional polyacrylamide gel electrophoretic method using two native gradient gels. Examination of the gel run at 0 degrees C in the second dimension showed the presence of four cold-dissociated proteins running below the diagonal and staining intensely with silver, in the extract of maize leaves. The electrophoretic method described here is expected to be a convenient way to detect cold-induced dissociation of soluble proteins in crude extracts of various tissues. It is also possible to estimate roughly the molecular weights of both the cold-dissociated subunit and the native protein from which it is derived.