Other names: PlantPIs, plantpis

Plant protease inhibitors (PIs) can be counted among the defensive proteins that plants display to minimize the adverse effects deriving from the attack of phytophagous insects. They are usually present in seeds and storage tissues, but are also expressed in the aerial part of plant upon insect attack. Their activity on gut proteases attenuates amino acid assimilation and slows the growth of feeding insects. Owing to the direct defensive properties of PIs, several transgenic plants have been produced expressing specific inhibitors and tested for enhanced resistance against phytophagous insects. Even if this approach revealed effective in many cases, it also gave the opportunity to demonstrate the capacity of some insects to overcome the effect of PI ingestion by up-regulating the synthesis of new proteases, insensitive to PIs. In this respect, structural studies on PIs and protease-PI complexes are needed to better understand the molecular mechanism of protease resistance and to put the basis for designing new PIs active toward insensitive proteases. Among plant PIs, inhibitors active toward the four mechanistic classes of proteases (serine-, cysteine-, aspartic- and metallo-proteases) have been described. The activity of PIs is due to their capacity to form stable complexes with target proteases, blocking, altering or preventing access to the enzyme active site. Plant PIs can also be catalogued in a number of families on the basis of their primary structure. Many of these families contain PIs specific for a single mechanistic class of proteases, but this does not seem to be a rule. PLANT-PIs is a database developed to facilitate retrieval of information on plant PIs and their genes. The need for a database comes from the large amount of sequences available and the increasing amount of data concerning the activity and structure of these molecules. The database correlates information contained in primary sequence databases (EMBL and SwissProt) to functional analysis of the proteins reported in literature. For each PI links to sequence databases are reported together with a summary of the functional properties of the molecule (and its mutants) as deduced from literature. Transgenic plants obtained transferring PI genes are also reported as deduced from literature. PLANT-PIs, as up-dated in July 2002, contains information for 495 inhibitors, plus several isoinhibitors, identified over 129 plant species. The database is accessible at http://bighost.area.




protein sequence protein family plant plant plant biology gene and protein families

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