AtCYS1, a cystatin from Arabidopsis thaliana, suppresses hypersensitive cell death.
In plants, cysteine protease inhibitors are involved in the regulation of protein turnover and play an important role in resistance against insects and pathogens. AtCYS1 from Arabidopsis thaliana encodes a protein of 102 amino acids that contains the conserved motif of cysteine protease inhibitors belonging to the cystatin superfamily (Gln-Val-Val-Ala-Gly). Recombinant A. thaliana cystatin-1 (AtCYS1) was expressed in Escherichia coli and purified. AtCYS1 inhibits the catalytic activity of papain (Kd = 4.0 x 10-2 micro m, at pH 7.0 and 25 degrees C), generally taken as a molecular model of cysteine proteases. The molecular bases for papain inhibition by AtCYS1 have been analysed taking into account the three-dimensional structure of the papain-stefin B complex. AtCYS1 is constitutively expressed in roots and in developing siliques of A. thaliana. In leaves, AtCYS1 is strongly induced by wounding, by challenge with avirulent pathogens and by nitric oxide (NO). The overexpression of AtCYS1 blocks cell death activated by either avirulent pathogens or by oxidative and nitrosative stress in both A. thaliana suspension cultured cells and in transgenic tobacco plants. The suppression of the NO-mediated cell death in plants overexpressing AtCYS1 provides the evidence that NO is not cytotoxic for the plant, indicating that NO functions as cell death trigger through the stimulation of an active process, in which cysteine proteases and theirs proteinaceous inhibitors appear to play a crucial role.
Belenghi
Beatrice
B
Dipartimento Scientifico e Tecnologico, Università degli Studi di Verona, Verona, Italy.
Acconcia
Filippo
F
Trovato
Maurizio
M
Perazzolli
Michele
M
Bocedi
Alessio
A
Polticelli
Fabio
F
Ascenzi
Paolo
P
Delledonne
Massimo
M
D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000166:cytology* / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000737:chemistry* / Q000378:metabolism; D001483:Base Sequence; D016923:Cell Death; D002478:Cells, Cultured; D003001:Cloning, Molecular; D017124:Conserved Sequence; D015891:Cystatins / Q000737:chemistry* / Q000378:metabolism; D015853:Cysteine Proteinase Inhibitors / Q000737:chemistry / Q000378:metabolism; D017931:DNA Primers; D004926:Escherichia coli / Q000235:genetics; D006801:Humans; D008969:Molecular Sequence Data; D010206:Papain / Q000037:antagonists & inhibitors; D016133:Polymerase Chain Reaction; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid
D029681:Arabidopsis Proteins; D015891:Cystatins; D015853:Cysteine Proteinase Inhibitors; D017931:DNA Primers; D011994:Recombinant Proteins; D010206:Papain