Proteinaceous inhibitors of endo-beta-glucanases |
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Authors: | York William S Qin Qiang Rose Jocelyn K C |
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Institution: | Department of Biochemistry and Molecular Biology, Complex Carbohydrate Research Center, University of Georgia, 220 Riverbend Road, Athens, GA 30602-4712, USA. will@ccrc.uga.edu |
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Abstract: | Both plants and filamentous phytopathogens secrete proteins that inhibit endo-beta-glucanases. The first endo-beta-glucanase inhibitor proteins to be discovered are XEGIP, a tomato protein that inhibits fungal xyloglucan-specific endo-beta-1,4-glucanases, and GIP1, an oomycete protein that inhibits endo-beta-1,3-glucanases produced by the plant host. These inhibitor proteins act by forming high-affinity complexes with their endoglucanase ligands. A family of XEGIP-like proteins has been identified. At least one member of this family (extracellular dermal glycoprotein, EDGP) has been shown to have endoglucanase-inhibitor activity, while other members have sequence similarity to a xylanase inhibitor from wheat (TAXI-1). The oomycete inhibitor GIP1 is a catalytically inactive serine protease homolog (SPH) whose structure is unrelated to XEGIP. Both types of inhibitor proteins are likely to affect the interactions of plants with filamentous phytopathogens, and a basic model describing their roles in pathogenesis is proposed. |
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