Inhibition of protein synthesis in vitro by proteins from the seeds of Momordica charantia (bitter pear melon)

Abstract

1. A haemagglutinating lectin was purified from the seeds of Momordica charantia by affinity chromatography on Sepharose 4B and on acid-treated Sepharose 6B. It has mol.wt. 115 000 and consists of four subunits, of mol.wts. 30 500, 29 000, 28 500 and 27 000. 2. The lectin inhibits protein synthesis by a rabbit reticulocyte lysate with an ID50 (concentration giving 50% inhibition) of approx. 5 micrograms/ml. Protein synthesis by Yoshida ascites cells is partially inhibited by the lectin at a concentration of 100 micrograms/ml. 3. From the same seeds another protein was purified which has mol.wt. 23 000 and is a very potent inhibitor of protein synthesis in the lysate system, with an ID50 of 1.8 ng/ml. This inhibitor has no effect on protein synthesis by Yoshida cells, and has no haemagglutinating properties. 4. Artemia salina ribosomes preincubated with the lectin or with the inhibitor lose their capacity to perform protein synthesis. The proteins seem to act catalytically, since they inactivate a molar excess of ribosomes. 5. The lectin and the inhibitor are somewhat toxic to mice, the LD50 being 316 and 340 micrograms/100 g body wt. respectively.

Selective cytotoxic activity of immunotoxins composed of a monoclonal anti-Thy 1.1 antibody and the ribosome-inactivating proteins bryodin and momordin

“…Bryodin gave an IC50 of 4.5 x 10 -I M consistent with the value originally reported . The momordin preparation used in these experiments had an IC50 of 2.2 x 10 -10M, slightly higher than previously measured (Barbieri et al, 1980). The capacity of 2-pyridyldithiopropionylated bryodin to inhibit protein synthesis in the reticulocyte lysate assay was almost entirely preserved after conjugation to antibody (Table I).…”

“…In the present study, we describe the preparation and properties of immunotoxins made by linking the monoclonal anti-Thy 1.1 antibody OX7 to two other RIPs: bryodin from the roots of Bryonia dioica and momordin, previously referred to as Momordica charantia inhibitor (Barbieri et al, 1980 (Chester, UK). N-succinimidyl 3-(2-pyridyldithio)propionate (SPDP) was from Pharmacia Ltd., (London, UK).…”

“…Momordin was purified as previously (Barbieri et al, 1980) except that the method was adapted to allow the processing of 500 g of seeds at a time. When examined by SDS-PAGE, it appeared as a single protein band (apparent Mr, 31,000) with traces of a contaminant protein with lower Mr.…”

“…Purification of RIPs Bryodin was purified by the procedure described previously ) and appeared as a single protein band (apparent Mr, 30,000) when analysed by SDS-PAGE. Momordin was purified as previously (Barbieri et al, 1980) except that the method was adapted to allow the processing of 500 g of seeds at a time. When examined by SDS-PAGE, it appeared as a single protein band (apparent Mr, 31,000) with traces of a contaminant protein with lower Mr.…”

MAP 30: a new inhibitor of HIV‐1 infection and replication

“…The fruit and seed extracts of MC have been used in China for centuries for anti-viral, antitumor and immunopotentiating purposes [ 11. In recent years, several proteins have been isolated from the seed extracts of this plant [2]. These proteins belong to the family of single chain ribosome-inactivating proteins.…”