An allergenic 2S storage protein from Ricinus communis seeds which is a part of the 2S albumin precursor predicted by c-DNA data.

1. A 1.9S albumin having allergenic activity and denoted Ric c III was isolated from an alcohol extract of defatted Ricinus communis seeds, CB-1A, as a homogeneous protein by ion-exchange chromatography on SP-Sephadex, gel filtration on Sephadex G-75 and preparative polyacrylamide gel electrophoresis (6 mg Ric c III/g CB-1A). 2. The protein contained approximately 98 amino acid residues distributed in 2 chains of 67 and 34 residues, a molecular weight of 11,239 based on amino acid composition and pI = 4.9 Ric c III can be aligned, on the basis of amino acid composition and partial amino acid sequence data, with residues 18 to 50 (51) and 66 to 130 of the 2S albumin precursor predicted by the cDNA data of S.D. Irwin, J.N. Keen, J.B.C. Findlay and J.M. Lord (Molecular and General Genetics, 222: 400-408, 1990). 3. The present data identify Ric c III as the second allergenic 2S storage albumin coded by this DNA.