Abstract
The chemical characteristics of α-momorcharin (α-M), β-momorcharin (β-M), and trichosanthin
(T), proteins with abortifacient, immunosuppressive, and antitumor activities, are
compared. The molecular masses of α-M, β-M, and T are respectively 29 000, 28 000
and 26 000. The former two are glycoproteins with a neutral sugar content of, respectively,
1.6% and 1.3%, while the latter is a non-glycoprotein. All three proteins carry Asp
at the NH2-terminus, and they are rich in Asp/Asn and Glu/Gln residues, but do not possess Cys
residues. α-M and T have a low methionine content while β-M is totally lacking in
methionine residues. Partial sequencing of α-M and T at the NH2-terminus reveals seven identical residues out of the twelve examined in the two proteins.
Cyanogen bromide digestion of α-M and T yields several fragments but β-M does not
yield any fragments upon digestion. Digestion of the proteins with proteases produces
different patterns of peptide fragments as revealed by SDS-polyacrylamide gel electrophoresis.
The immunoprecipitin arcs formed in immunodiffusion between the proteins and their
antisera intersect one another.
