• Applied Biological Chemistry
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• v.38 no.6
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• pp.528-533
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• 1995

An antiviral protein (AAP29) with ribosome-inactivating activity was purified and characterized from the leaves of the Amaranthus mangostanus. Purification was accomplished through crude extraction, ammonium sulfate precipitation, S-Sepharose chromatography, gel filtration, CM-Sepharose chromatography and Blue sepharose chromatography. This protein was about 29.2 kDa and strongly basic with the PI value between 9.0 and 9.6, indicating that AAP29 is similar to Type 1 RIP. The AAP29 showed high thermostability without activity toss even after 20 min at $50^{\circ}C$. In cell free system using rabbit reticulocyte lysate, AAP29 inhibited protein synthesis with an $IC_{50}$, of 0.18 nM. This protein also reduced mosaic symptoms of cucumber mosaic virus (CMV) on tobacco leaves. The N-terminal amino acid sequences of the AAP29 are ADLTFTVTKDGTSQSYXTLXNXWRXW and shows no sequence similarity with any known RIPs.

• Applied Biological Chemistry
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• v.40 no.5
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• pp.375-379
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• 1997

Two ribosome-inactivating proteins, PRIP 1 and PRIP 2 have been isolated from the leaves of $Cucurbita\;moschata\;D_{UCHESNE}$. Crude extracts were purified through ammonium sulfate precipitation and column chromatography using DE-52 cellulose, S-Sepharose, FPLC Suprose 12 HR and FPLC Mono-S. The molecular weights of PRIP 1 and PRIP 2 were 31,000 and 30,500, respectively. PRIP 2 was thermostabe and maintained its activity even after the incubation of the protein at $50^{\circ}C$ for 30 min. In a cell free in vitro translation system using rabbit reticulocyte lysate, protein synthesis was inhibited by the addition of PRIP 1 and PRIP 2. The $IC_{50}$ of PRIP 1 and PRIP 2 were 0.82 nM and 0.79 nM, respectively. The comparison of N-terminal amino acid sequences of the PRIP 1 and PRIP 2 with known RIPs revealed that PRIP 1 shows sequence similarity with Luffin B from Luffa cylindrica and Trichokirin from Trichosanthes kirilowii Maximowicz and PRH) 2 has sequence similarity with Momordin II and MAP 30 from Momordica charantia.