Vol. 116, No. 3, 1983 November 15, 1983 BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS Pages 1049-1055 POSTTRANSLATIONAL MODIFICATION OF HUMAN T-CELL GROWTH FACTOR Richard J. Robb, RuSty M. Kutny, Maria Panico*, Howard Morris*, William F. DeGrado, and Vinay Chowdhry Central Research and Development Department, E.I. du Pont de Nemours and Company, Wilmington, DE 19036 *Department of Biochemistry, Imperial College, London SW7, England Received October 3, 1983 Amino-terminal sequence analysis of human T-cell growth factor indicated that the amino acid in position 3 of the polypeptide chain was modified. Examination of the N-terminal octapeptide using the amino acid analyzer and mass spectrometry demonstrated that position 3 was a threonine which was linked to N-acetyl-D- galactosamine. This site of glycosylation is of practical significance since it appears to play a role in the selectivity of a monoclonal antibody for the factor. T-cell growth factor (TCGF) I, also known as Interleukin 2, provides a signal for the proliferation of activated T-cells during the T-cell immune response (1-3). The factor has been used widely for the maintainance and cloning of non-transformed T-cells in culture (2,4,5). In addition to its use in the laboratory, several studies have indicated that defects in TCGF or its production may be involved in certain pathological states (6-9). A complete structural characterization of this lymphokine will thus be valuable to an understanding of both the T-cell response and the factor's potential clinical utility. Using conventional biochemical demonstrated that TCGF is a 15000MW modification with a variable degree of approaches, it was protein subject to glycosylation (I0). Although there was no evidence that the carbohydrate affected in vitro bioactivity, it was postulated that it might affect the iT-cell growth factor, TCGF; phenylthiohydantoin, PTH; synthetic decapeptide, Syn-P. 1049 0006-291X/83 $1.50 Copyright © 1983 by Academic Press, Inc. All rights of reproduction in any form reserved.