1. Yeast‐based reporter assay system for identifying the requirements of intramembrane proteolysis by signal peptide peptidase of Arabidopsis thaliana
- Author
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Tomiko Asakura, Tomoko Tamura, Tatsuya Maeda, Kenta Kusunoki, Keiko Abe, and Masako Hoshi
- Subjects
0301 basic medicine ,Signal peptide ,Proteolysis ,Mutant ,Arabidopsis ,Saccharomyces cerevisiae ,General Biochemistry, Genetics and Molecular Biology ,intramembrane cleavage ,03 medical and health sciences ,0302 clinical medicine ,Gene expression ,medicine ,Aspartic Acid Endopeptidases ,lcsh:QH301-705.5 ,Research Articles ,Reporter gene ,yeast‐based reporter assay ,medicine.diagnostic_test ,Chemistry ,C-terminus ,food and beverages ,helix breaker ,Transmembrane domain ,endoplasmic reticulum ,030104 developmental biology ,Biochemistry ,lcsh:Biology (General) ,030220 oncology & carcinogenesis ,signal peptide peptidase ,Signal peptide peptidase ,Research Article - Abstract
We constructed a yeast‐based reporter assay system to verify the cleavage activity of Arabidopsis thaliana signal peptide peptidase, a transmembrane protease localized in the endoplasmic reticulum. Arabidopsis thaliana signal peptide peptidase cleaved 15 candidate substrates that lacked the positively charged amino acids, His and Lys, in the C‐region of signal peptides. Our assay system may be suitable for identifying innate substrates with crucial roles in plants., Signal peptide peptidase (SPP) is an aspartic protease with two active sites, YD and GXGD, in the transmembrane domain. SPP cleaves signal peptides, and the released fragments play key roles in the immune system, embryo development and protein turnover in cells. Despite SPP having an important function, a general system to identify the requirements of intramembrane proteolysis by SPP has not been developed because proteolysis occurs in the membrane. In this study, we first established a reporter assay system in yeast to verify the cleavage activity of the Arabidopsis thaliana SPP (AtSPP). Next, we screened candidate substrates of AtSPP from A. thaliana pollen and roots. In the pollen, 13 signal peptides with 'pollen' and 'cell wall' as gene ontology terms were selected. In the roots, mutants overexpressing AtSPP were constructed, and gene expression changes were compared with the wild‐type. Nine signal peptides expressed in the roots were selected. Then we used the candidate substrates in our reporter assay system to determine the requirements for proteolysis by AtSPP. Fifteen of 22 signal peptides were cleaved by AtSPP. The absence of the positively charged amino acids, His and Lys on the C terminus of the signal sequence, was observed in cleaved substrates. Moreover, mutation of a helix breaker‐to‐Leu substitution in the intramembrane region in substrates prevented cleavage by AtSPP. These results indicated that substrates of AtSPP required the helix breaker structure to be cleaved.
- Published
- 2020