Proteinaceous inhibitors of endo-β-glucanases
2004
York, W.S. | Qin, Q. | Rose, J.K.C.
Both plants and filamentous phytopathogens secrete proteins that inhibit endo-β-glucanases. The first endo-β-glucanase inhibitor proteins to be discovered are XEGIP, a tomato protein that inhibits fungal xyloglucan-specific endo-β-1,4-glucanases, and GIP1, an oomycete protein that inhibits endo-β-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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