Polygalacturonase-inhibiting protein interacts with pectin through a binding site formed by four clustered residues of arginine and lysine

Sara Spadoni, Olga Zabotina, Adele Di Matteo, Jørn Dalgaard Mikkelsen, Felice Cervone, Giulia De Lorenzo, Benedetta Mattei, Daniela Bellincampi

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

Polygalacturonase-inhibiting protein ( PGIP) is a cell wall protein that inhibits fungal polygalacturonases ( PGs) and retards the invasion of plant tissues by phytopathogenic fungi. Here, we report the interaction of two PGIP isoforms from Phaseolus vulgaris ( PvPGIP1 and PvPGIP2) with both polygalacturonic acid and cell wall fractions containing uronic acids. We identify in the three-dimensional structure of PvPGIP2 a motif of four clustered arginine and lysine residues ( R183, R206, K230, and R252) responsible for this binding. The four residues were mutated and the protein variants were expressed in Pichia pastoris. The ability of both wild-type and mutated proteins to bind pectins was investigated by affinity chromatography. Single mutations impaired the binding and double mutations abolished the interaction, thus indicating that the four clustered residues form the pectin-binding site. Remarkably, the binding of PGIP to pectin is displaced in vitro by PGs, suggesting that PGIP interacts with pectin and PGs through overlapping although not identical regions. The specific interaction of PGIP with polygalacturonic acid may be strategic to protect pectins from the degrading activity of fungal PGs.
Original languageEnglish
JournalPlant Physiology
Volume141
Issue number2
Pages (from-to)557-564
ISSN0032-0889
DOIs
Publication statusPublished - 2006
Externally publishedYes

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