title: Isolation and characterization of proteinase inhibitor I from etiolated tobacco leaves.
abstract: Proteinase Inhibitor I was induced to accumulate in tobacco (Nicotiana tabaccum) leaves by placing plants in darkness for 10 days at 27 degrees C. The inhibitor was isolated using ammonium sulfate precipitation, Sephadex G-75 chromatography, heating, and affinity chromatography with a chymotrypsin-Sepharose column. Inhibitor I was purified 232-fold with a yield of 34 mg from 2.5 kg of leaves. Affinity-purified tobacco Inhibitor I was shown to be homogeneous by gel electrophoresis in both nondissociating and dissociating buffers. The inhibitor has a molecular weight of 39,000 +/- 1000 determined by gel filtration and, like its potato and tomato counterparts, is composed of five subunits of molecular weight 8100. The tobacco Inhibitor I strongly inhibits chymotrypsin and weakly inhibits trypsin. The chemical, physical, and immunological properties of tobacco Inhibitor I indicate that it is structurally very similar to potato tuber Inhibitor I and tomato leaf Inhibitor I, although the synthesis and accumulation of the three inhibitors in their respective tissues are all under different developmental or environmental regulation.
mesh_terms: D055598:Chemical Phenomena; D002621:Chemistry; D002846:Chromatography, Affinity; D004589:Electrophoresis, Disc; D005779:Immunodiffusion; D007122:Immunoelectrophoresis; D008970:Molecular Weight; D010940:Plant Proteins / Q000302:isolation & purification*; D010947:Plants, Toxic; D011480:Protease Inhibitors / Q000302:isolation & purification*; D014026:Nicotiana / Q000032:analysis*
chemical_list: D010940:Plant Proteins; D011480:Protease Inhibitors; C023578:proteinase inhibitor I (plants)