Cellular and subcellular distribution of saporins, type-1 ribosome-inactivating proteins, in soapwort (Saponaria officinalis L.)

The ribosome-inactivating proteins (RIPs) are a family of plant enzymes for which a unique activity has been determined: rRNA N-glycosidase, which removes adenine at a specific universally conserved position (A4324 in the case of rat ribosomes). Here we report that saporin-L1, a RIP from the leaves of Saponaria officinalis, recognizes other substrates, including RNAs from different sources, DNA and poly(A). Saporin-L1 depurinated DNA extensively and released adenine from all adenine-containing polynucleotides tested. Adenine was the only base released from DNA or artificial polynucleotides. The characteristics of the reactions catalysed by saporin-L1 have been determined: optimal pH and temperature, ionic requirements, and the kinetic parameters Km and kcat. The reaction proceeded without cofactors, at low ionic strength, in the absence of Mg2+ and K+. Saporin-L1 had no activity towards various adenine-containing non-polynucleotide compounds (cytokinins, cofactors, nucleotides). This plant protein may now be classified as a polynucleotide:adenosine glycosidase.

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Quinoa as source of type 1 ribosome inactivating proteins: A novel knowledge for a revision of its consumption

Food Chemistry ◽

10.1016/j.foodchem.2020.128337 ◽

2020 ◽

pp. 128337

Author(s):

Nicola Landi ◽

Maria Rosaria Ruocco ◽

Sara Ragucci ◽

Federica Aliotta ◽

Rosarita Nasso ◽

...

Keyword(s):

Ribosome Inactivating Proteins

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Genotoxic Stress and Cellular Stress Alter the Subcellular Distribution of Human T-Cell Leukemia Virus Type 1 Tax through a CRM1-Dependent Mechanism

Journal of Virology ◽

10.1128/jvi.02270-05 ◽

2006 ◽

Vol 80 (13) ◽

pp. 6657-6668 ◽

Cited By ~ 14

Author(s):

Michael L. Gatza ◽

Susan J. Marriott

Keyword(s):

Subcellular Distribution ◽

Leukemia Virus ◽

Cellular Stress ◽

Genotoxic Stress ◽

Cellular Proteins ◽

Cell Leukemia ◽

Cell Leukemia Virus Type ◽

Human T Cell ◽

T Cell Leukemia Virus

ABSTRACT Human T-cell leukemia virus type 1 Tax is a predominantly nuclear viral oncoprotein that colocalizes with cellular proteins in nuclear foci known as Tax speckled structures (TSS). Tax is also diffusely distributed throughout the cytoplasm, where it interacts with and affects the functions of cytoplasmic cellular proteins. Mechanisms that regulate the distribution of Tax between the cytoplasm and nucleus remain to be identified. Since Tax has been shown to promote genome instability by perturbing cell cycle progression and DNA repair mechanisms following DNA damage, we examined the effect of genotoxic stress on the subcellular distribution and interacting partners of Tax. Tax localization was altered in response to various forms of cellular stress, resulting in an increase in cytoplasmic Tax and a decrease in Tax speckled structures. Concomitantly, colocalization of Tax with sc35 (a TSS protein) decreased following stress. Tax translocation required the CRM1 nuclear export pathway, and a transient interaction between Tax and CRM1 was observed following stress. These results suggest that the subcellular distribution of Tax and the interactions between Tax and cellular proteins respond dynamically to cellular stress. Changes in Tax distribution and interacting partners are likely to affect cellular processes that regulate cellular transformation.

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