InterPro domain: IPR038408

Ginkbilobin-2 (Gnk2) is an antifungal protein found in the endosperm of Ginkgoseeds, which inhibits the growth of phytopathogenic fungi such as Fusariumoxysporum. Gnk2 has considerable homology (~85%) to embryo-abundant proteins(EAP) from the gymnosperms Picea abies and P. glauca. Plant EAP are expressedin the late stage of seed maturation and are involved in protection againstenvironmental stresses such as drought. The sequence of Gnk2 is also 28-31%identical to the extracellular domain of cysteine-rich receptor-like kinases(CRK) from the angiosperm Arabidopsis. The CRK members are induced by pathogeninfection and treatment with reactive oxygen species or salicylic acid and areinvolved in the hypersensitive reaction, which is a typical system ofprogrammed cell death. In addition, there are at least 60 genes in Arabidopsisencoding the cysteine-rich secreted proteins (CRSP) with an Gnk2-homologousdomain. Therefore, the proteins with a Gnk2-homologous domain are regarded asone of the largest protein superfamilies, although the role of the conservedGnk2-homologous domain remains unclear [ 1 , 2 ].The Gnk2-homologous domain is composed of two alpha-helices and a fivestranded beta-sheet, which forms a compact single-domain architecture with analpha+beta-fold. It contains a C-X(8)-C-X(2)-C motif.Cysteine residues form three intramolecular disulphide bridges: C1-C5, C2-C3,and C4-C6 [ 3 ].

1. Crystal structure of ginkbilobin-2 with homology to the extracellular domain of plant cysteine-rich receptor-like kinases. Proteins 77, 247-51
2. A superfamily of proteins with novel cysteine-rich repeats. Plant Physiol. 126, 473-6