摘要
Plant cystatins or phytocystatins are cysteine proteinase inhibitors exist widely in different plant species. Because they can kill insects by inhibiting the digestive function of the cysteine proteinase in gut, they are believed to play an important role in plant’s defense against pests. Phytocystatins contain the conserved QXVXG motif and show some features on their sequence different to animal cystatins. After sequencing the protein directly and the cDNA clone, a large number of plant cystatins have been characterized. A multialignment with BLAST software and a detail analysis of 38 phytocystatins show that phytocystatins possess a specific conserved amino acid sequence [LRVI]-[AGT]-[RQKE]-[FY]- [AS]-[VI]-X-[EGHDQV]-[HYFQ]-N different to the conserved sequence demonstrated by Margis in 1998. This conserved sequence can be enough to detect with exclusivity phytocystatin sequences on protein data banks. A classification of these phytocystatins is performed and they can be divided into 3 groups according to their features on amino acid sequence, and the group-I can be still divided into 3 subgroups based on the feature of their amino acid and genomic sequence. By the CLUSTALX software, the most conserved nucleotide sequences of phytocystatins were found, which could be used to design the degenerate premiers to search new phytocystatins with PCR reaction.
Plant cystatins or phytocystatins are cysteine proteinase inhibitors exist widely in different plant species. Because they can kill insects by inhibiting the digestive function of the cysteine proteinase in gut, they are believed to play an important role in plant’s defense against pests. Phytocystatins contain the conserved QXVXG motif and show some features on their sequence different to animal cystatins. After sequencing the protein directly and the cDNA clone, a large number of plant cystatins have been characterized. A multialignment with BLAST software and a detail analysis of 38 phytocystatins show that phytocystatins possess a specific conserved amino acid sequence [LRVI]-[AGT]-[RQKE]-[FY]- [AS]-[VI]-X-[EGHDQV]-[HYFQ]-N different to the conserved sequence demonstrated by Margis in 1998. This conserved sequence can be enough to detect with exclusivity phytocystatin sequences on protein data banks. A classification of these phytocystatins is performed and they can be divided into 3 groups according to their features on amino acid sequence, and the group-I can be still divided into 3 subgroups based on the feature of their amino acid and genomic sequence. By the CLUSTALX software, the most conserved nucleotide sequences of phytocystatins were found, which could be used to design the degenerate premiers to search new phytocystatins with PCR reaction.
基金
Supported by The National Basic Research Program (973 Program) ( G1999016003), Graduate Students’ Research Foundation of BeijingForestry University and the Key Laboratory for Silviculture and Conservation of Ministry of Education, Beijing Forestry University
