6ti2 | pdb_00006ti2
Structure of the Ustilago maydis chorismate mutase 1 in complex with KWL1-b from Zea mays
Structural highlights
FunctionCMU1_USTMA Secreted chorismate mutase that is one component of a cocktail of effectors shaping the host metabolome and acting as virulence factors. The enzyme is taken up by plant cells, can spread to neighboring cells where it affects the biosynthesis of the plant immune signal salicylic acid by channelling chorismate into the phenylpropanoid pathway (PubMed:21976020, PubMed:30651637). Interfers with the activity of host cytosolic chorismate mutase CM2 through heterodimerization (PubMed:21976020).[1] [2] Publication Abstract from PubMedMany plant-pathogenic bacteria and fungi deploy effector proteins that down-regulate plant defense responses and reprogram plant metabolism for colonization and survival in planta. Kiwellin (KWL) proteins are a widespread family of plant-defense proteins that target these microbial effectors. The KWL1 protein from maize (corn, Zea mays) specifically inhibits the enzymatic activity of the secreted chorismate mutase Cmu1, a virulence-promoting effector of the smut fungus Ustilago maydis. Besides KWL1, 19 additional KWL paralogs have been identified in maize. Here, we investigated the structure and mechanism of the closest KWL1 homolog, KWL1-b (ZEAMA_GRMZM2G305329). We solved the Cmu1-KWL1-b complex to 2.75 A resolution, revealing a highly symmetric Cmu1-KWL1-b heterotetramer in which each KWL1-b monomer interacts with a monomer of the Cmu1 homodimer. The structure also revealed that the overall architecture of the heterotetramer is highly similar to that of the previously reported Cmu1-KWL1 complex. We found that upon U. maydis infection of Z. mays, KWL1-b is expressed at significantly lower levels than KWL1 and exhibits differential tissue-specific expression patterns. We also show that KWL1-b inhibits Cmu1 activity similarly to KWL1. We conclude that KWL1 and KWL1-b are part of a redundant defense system that tissue-specifically targets Cmu1. This notion was supported by the observation that both KWL proteins are carbohydrate-binding proteins with distinct and likely tissue-related specificities. Moreover, binding by Cmu1 modulated the carbohydrate-binding properties of both KWLs. These findings indicate that KWL proteins are part of a spatiotemporally coordinated, plant-wide defense response comprising proteins with overlapping activities. The two paralogous kiwellin proteins KWL1 and KWL1-b from maize are structurally related and have overlapping functions in plant defense.,Altegoer F, Weiland P, Giammarinaro PI, Freibert SA, Binnebesel L, Han X, Lepak A, Kahmann R, Lechner M, Bange G J Biol Chem. 2020 Apr 28. pii: RA119.012207. doi: 10.1074/jbc.RA119.012207. PMID:32350112[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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