Am. Saboori et al., TRYPTIC PEPTIDES OF HUMAN THYROGLOBULIN .1. IMMUNOREACTIVITY WITH MURINE MONOCLONAL-ANTIBODIES, Clinical and experimental immunology, 98(3), 1994, pp. 454-458
Human thyroglobulin (Tg) was treated with trypsin at different concent
rations of trypsin/Tg for various incubation times at 37 degrees C usi
ng non-reducing conditions. A ratio of trypsin to Tg of 1:100 (w/w) wa
s optimal to release small peptides that were reactive to murine MoAbs
to human Tg. Most peptides were released after only 1 h incubation wi
th trypsin, but these peptides were further degraded at longer incubat
ion times. However, a few small peptides, the largest of which with an
apparent molecular weight (MW(ap)) of 40 kD, resisted tryptic digesti
on up to at least 12 h of incubation. These resistant peptides were fu
rther degraded by trypsin at 18-24 h of incubation. Tryptic peptides o
f Tg, released at 1 h and 4 h of incubation, were analysed for their i
mmunoreactivity to 16 well characterized anti-Tg MoAbs by Western immu
noblot. Patterns of peptide recognition of these MoAbs were generally
unique. Eight MoAbs reacted with peptides of MW(ap) of 10-25 kD and ab
ove. Four other MoAbs reacted with peptides of MW(ap) of 25-43 kD and
above, and the remaining four reacted with peptides of MW(ap) > 43 kD.
Nine of these MoAbs failed to recognize peptides after reduction, sug
gesting that the MoAbs bind conformation-dependent epitopes. The above
information will promote the development of models relating the struc
ture of Tg to the autoimmune process, and may provide an understanding
of those regions of Tg responsible for the induction of autoimmune th
yroiditis.