Retraction concerning the E2 protein of human papillovirus type 16: overexpression and purification of an active transcriptional regulator [Lees, M.E., Dreissen, H.P.C., Crawford, L.V. & Clarke, A.R. (1990) Eur. J. Biochem. 190, 85-92.] Expression of the human papillovirus type 16 E2 protein in Escherichia coli.