4ILT

Structure of the dioxygenase domain of SACTE_2871, a novel dioxygenase carbohydrate-binding protein fusion from the cellulolytic bacterium Streptomyces sp. SirexAA-E

Summary for 4ILT

• Entry DOI: 10.2210/pdb4ilt/pdb
• Related: 4ILV 4ILY 4IM1 4IM4
• Descriptor: Intradiol ring-cleavage dioxygenase, FE (III) ION, CHLORIDE ION, ... (4 entities in total)
• Functional Keywords: iron center, intradiol dioxygenase, carbohydrate binding domain, oxidoreductase
• Biological source: Streptomyces sp. SirexAA-E
• Total number of polymer chains: 4
• Total formula weight: 67073.30

Authors

Bianchetti, C.M.,Takasuka, T.E.,Bergeman, L.F.,Harmann, C.H.,Fox, B.G. (deposition date: 2012-12-31, release date: 2013-05-15, Last modification date: 2017-11-15)

Primary citation

Bianchetti, C.M.,Harmann, C.H.,Takasuka, T.E.,Hura, G.L.,Dyer, K.,Fox, B.G.
Fusion of Dioxygenase and Lignin-binding Domains in a Novel Secreted Enzyme from Cellulolytic Streptomyces sp. SirexAA-E.
J.Biol.Chem., 288:18574-18587, 2013

PubMed Abstract: Streptomyces sp. SirexAA-E is a highly cellulolytic bacterium isolated from an insect/microbe symbiotic community. When grown on lignin-containing biomass, it secretes SACTE_2871, an aromatic ring dioxygenase domain fused to a family 5/12 carbohydrate-binding module (CBM 5/12). Here we present structural and catalytic studies of this novel fusion enzyme, thus providing insight into its function. The dioxygenase domain has the core β-sandwich fold typical of this enzyme family but lacks a dimerization domain observed in other intradiol dioxygenases. Consequently, the x-ray structure shows that the enzyme is monomeric and the Fe(III)-containing active site is exposed to solvent in a shallow depression on a planar surface. Purified SACTE_2871 catalyzes the O2-dependent intradiol cleavage of catechyl compounds from lignin biosynthetic pathways, but not their methylated derivatives. Binding studies show that SACTE_2871 binds synthetic lignin polymers and chitin through the interactions of the CBM 5/12 domain, representing a new binding specificity for this fold-family. Based on its unique structural features and functional properties, we propose that SACTE_2871 contributes to the invasive nature of the insect/microbial community by destroying precursors needed by the plant for de novo lignin biosynthesis as part of its natural wounding response.

PubMed: 23653358
DOI: 10.1074/jbc.M113.475848

Experimental method

X-RAY DIFFRACTION (2.55 Å)