Studies of the subunit structure of wheat germ ribonucleic acid polymerase II

We have previously presented a rapid, high yield method for the large scale purification of homogeneous RNA polymerase II from wheat germ (Jendrisak, J.J., and Burgess, R.R.(1975), Biochemistry 14, 4639), and we now report a detailed study of its subunit structure. Polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate indicates that polypeptides with molecular weights of 220 000, 140 000, 40 000, 27 000, 25 000, 21 000, 20 000, 17 800, 17 000, 16 500, 16 000, and approximately 14 000 are associated with the enzyme. Two-dimensional polyacrylamide gel electrophoresis, by which the subunits were separated in the first dimension in the presence of 8 M urea at pH 8.7 and in the second dimension in the presence of 0.1% sodium dodecyl sulfate, indicates that the 40 000 molecular weight component is composed of two nearly identical polypeptides and that the low molecular weight components (smaller than or equal to 40 000) are acidic proteins except for the 25 000 molecular weight polypeptide.