title: Specificity of protein turnover in tomato leaves. Accumulation of proteinase inhibitors, induced with the wound hormone, PIIF.
abstract: Detached tomato leaves, supplied with the proteinase inhibitor inducing factor (PIIF) and incubated with water under constant light, exhibited a specificity of intracellular protein turnover directed toward the selective accumulation of heat-stable proteins having disulfide corss-linkages. Approximately 70% of the accumulated proteins could be accounted for in two proteinase inhibitors rich in disulfide links. The accumulation of proteins containing disulfides was accompanied by a net loss in total leaf protein, mainly of heat-precipitable proteins having free sulfhydryl residues. Relative rates of synthesis of --S--S-- proteins and --SH proteins were assessed by comparing rates of incorporation of isotope into the inhibitor proteins and noninhibitor leaf proteins. Although the inhibitors represented about 12% of total leaf protein after 71 h of induction, only about 2% of total protein synthesis was directed toward inhibitor synthesis during incubation of induced leaves. The marked stability of inhibitors, and other disulfide proteins against degradation in vivo, appeared to be a major factor providing for their selective accumulation. It was concluded that the state of oxidation of protein-bound half-cystine residues may be a principle parameter influencing the susceptibility of leaf proteins to degradation in vivo.
mesh_terms: D001665:Binding Sites; D004220:Disulfides / Q000378:metabolism; D004355:Drug Stability; D004791:Enzyme Inhibitors / Q000378:metabolism*; D006358:Hot Temperature; D007700:Kinetics; D010940:Plant Proteins / Q000302:isolation & purification / Q000378:metabolism* / Q000494:pharmacology; D010944:Plants / Q000378:metabolism; D011480:Protease Inhibitors; D011485:Protein Binding; D011487:Protein Conformation; D012995:Solubility; D013438:Sulfhydryl Compounds / Q000378:metabolism
chemical_list: D004220:Disulfides; D004791:Enzyme Inhibitors; D010940:Plant Proteins; D011480:Protease Inhibitors; D013438:Sulfhydryl Compounds