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For the elucidation of the amino-acid sequence of the carboxyl-terminal region of soybean trypsin inhibitor (Kunitz), fragments C and D were digested with trypsin, and the resulting peptides were separated by ion-exchange chromatography on Dowex 50X2 or by gel filtration on Bio-Gel P-4. Further fractionation and purification of the peptides were performed by ion-exchange chromatography on Dowex 1X2, by gel filtration on Bio-Gel P-2 or by high-voltage paper electrophoresis at pH 1.9 and 3.6. Three peptides were obtained in pure form from fragment C and ten peptides from fragment D, and their amino-acid sequences were determined by the direct Edman method and by carboxy- peptidase digestion technique. Overlapping peptides necessary for the alignment of the tryptic peptides from fragment D were obtained from a chymotryptic hydrolysate of fragment D. Nine main peptides and rune minor peptides were obtained. The amino acid composition and the partial amino-acid sequence of the 18 chymotryptic peptides of fragment D made it possible to establish the amino-acid sequence of the carboxyl-terminal region of the inhibitor. The complete amino-acid sequence of soybean trypsin inhibitor (Kunitz) deduced here was compared with that of Bowman-Birk inhibitor, another well-known soybean proteinase inhibitor. [ABSTRACT FROM AUTHOR]

The complete amino acid sequence of the u chain of the mitogenic lectin from Vicia sativa has been determined. The polypeptide was digested by trypsin and chymotrypsin. The fragments were isolated and most of them were sequenced by automatic solid-phase Edman degradation. A total sequence of 52 amino acid residues was obtained which is homologous to the α subunits of the lectins from Pisum sativum, Lens culinaris and Vicia faba. The central part (residues 13–32) in particular is completely conserved in all four proteins. In contrast to the three other known sequences, the V. sativa α subunit has an additional serine at the N terminus. The differences of the related amino acid sequences of these lectins and concanavalin A, the lectin from Canavalia ensiformis, have been compared using the relative substitution frequency found in homologous proteins by McLachlan. The degree of homology decreases in the order: V. sativa > P. sativum > V. faba > L. culinaris > C. ensiformis. Prediction of the secondary structure according to Chou and Fasman reveals that the lectin α chain is similar to concanavalin A in the first half of tile molecule whereas the C-terminal part apparently tends to form an α helix. [ABSTRACT FROM AUTHOR]