Isolation and characterization of a cDNA that encodes a novel proteinase inhibitor I from a tobacco genetic tumor.
We have isolated a cDNA clone, designated GTI, by screening a tobacco genetic tumor cDNA library with a tumor-specific "subtracted" cDNA probe. The cDNA contained the entire coding sequence for a 94-amino-acid polypeptide that exhibited significant homology to members of the proteinase inhibitor I family from tomato and potato. The predicted protein has a pre-sequence of 22 amino acids but lacks a pro-sequence, unlike genes for proteinase inhibitor I isolated to date. Furthermore, the protein encoded by GTI cDNA has a novel reactive site, having glutamine as the P1 reactive residue. These results suggest that the GTI protein is a novel member of the proteinase inhibitor I family. The mRNA for GTI accumulated at a high level but only transiently after the wounding of tobacco plants. Thus, it appears that the GTI protein has a function that is related to the protection of tissues against damage due to wounding.
Department of Pure and Applied Sciences, University of Tokyo, Japan.
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Fujita
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Kouchi
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Ichikawa
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Syõno
D000595:Amino Acid Sequence; D001483:Base Sequence; D015139:Blotting, Southern; D003001:Cloning, Molecular; D015342:DNA Probes; D018076:DNA, Complementary / Q000302:isolation & purification / Q000378:metabolism; D015723:Gene Library; D008969:Molecular Sequence Data; D010940:Plant Proteins / Q000096:biosynthesis* / Q000235:genetics; D010941:Plant Tumors; D010947:Plants, Toxic; D017386:Sequence Homology, Amino Acid; D014026:Nicotiana / Q000235:genetics* / Q000378:metabolism
D015342:DNA Probes; D018076:DNA, Complementary; C088274:GTI protein, Nicotiana glauca; D010940:Plant Proteins