Structural highlights
FunctionPublication Abstract from PubMedTan spot of wheat (Triticum aestivum), caused by the fungus Pyrenophora tritici-repentis, has significant agricultural and economic impact. Ptr ToxA (ToxA), the first discovered proteinaceous host-selective toxin, is produced by certain P. tritici-repentis races and is necessary and sufficient to cause cell death in sensitive wheat cultivars. We present here the high-resolution crystal structure of ToxA in two different crystal forms, providing four independent views of the protein. ToxA adopts a single-domain, beta-sandwich fold of novel topology. Mapping of the existing mutation data onto the structure supports the hypothesized importance of an Arg-Gly-Asp (RGD) and surrounding sequence. Its occurrence in a single, solvent-exposed loop in the protein suggests that it is directly involved in recognition events required for ToxA action. Furthermore, the ToxA structure reveals a surprising similarity with the classic mammalian RGD-containing domain, the fibronectin type III (FnIII) domain: the two topologies are related by circular permutation. The similar topologies and the positional conservation of the RGD-containing loop raises the possibility that ToxA is distantly related to mammalian FnIII proteins and that to gain entry it binds to an integrin-like receptor in the plant host. Structure of Ptr ToxA: an RGD-containing host-selective toxin from Pyrenophora tritici-repentis.,Sarma GN, Manning VA, Ciuffetti LM, Karplus PA Plant Cell. 2005 Nov;17(11):3190-202. Epub 2005 Oct 7. PMID:16214901[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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