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Crystal structures of barley thioredoxin h isoforms HvTrxh1 and HvTrxh2 reveal features involved in protein recognition and possibly in discriminating the isoform specificity.

ABSTRACT: H-type thioredoxins (Trxs) constitute a particularly large Trx sub-group in higher plants. Here, the crystal structures are determined for the two barley Trx h isoforms, HvTrxh1 and HvTrxh2, in the partially radiation-reduced state to resolutions of 1.7 A, and for HvTrxh2 in the oxidized state to 2.0 A. The two Trxs have a sequence identity of 51% and highly similar fold and active-site architecture. Interestingly, the four independent molecules in the crystals of HvTrxh1 form two relatively large and essentially identical protein-protein interfaces. In each interface, a loop segment of one HvTrxh1 molecule is positioned along a shallow hydrophobic groove at the primary nucleophile Cys40 of another HvTrxh1 molecule. The association mode can serve as a model for the target protein recognition by Trx, as it brings the Met82 Cgamma atom (gamma position as a disulfide sulfur) of the bound loop segment in the proximity of the Cys40 thiol. The interaction involves three characteristic backbone-backbone hydrogen bonds in an antiparallel beta-sheet-like arrangement, similar to the arrangement observed in the structure of an engineered, covalently bound complex between Trx and a substrate protein, as reported by Maeda et al. in an earlier paper. The occurrence of an intermolecular salt bridge between Glu80 of the bound loop segment and Arg101 near the hydrophobic groove suggests that charge complementarity plays a role in the specificity of Trx. In HvTrxh2, isoleucine corresponds to this arginine, which emphasizes the potential for specificity differences between the coexisting barley Trx isoforms.

SUBMITTER: Maeda K

PROVIDER: S-EPMC2386739 | biostudies-literature | 2008 Jun

REPOSITORIES: biostudies-literature

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Crystal structures of barley thioredoxin h isoforms HvTrxh1 and HvTrxh2 reveal features involved in protein recognition and possibly in discriminating the isoform specificity.

Maeda Kenji K Hägglund Per P Finnie Christine C Svensson Birte B Henriksen Anette A

Protein science : a publication of the Protein Society 20080418 6

H-type thioredoxins (Trxs) constitute a particularly large Trx sub-group in higher plants. Here, the crystal structures are determined for the two barley Trx h isoforms, HvTrxh1 and HvTrxh2, in the partially radiation-reduced state to resolutions of 1.7 A, and for HvTrxh2 in the oxidized state to 2.0 A. The two Trxs have a sequence identity of 51% and highly similar fold and active-site architecture. Interestingly, the four independent molecules in the crystals of HvTrxh1 form two relatively lar ...[more]

PMID: 18424513

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Project description:BackgroundThe human mouth is a natural laboratory for studying how bacterial communities differ across habitats. Different bacteria colonize different surfaces in the mouth-teeth, tongue dorsum, and keratinized and non-keratinized epithelia-despite the short physical distance between these habitats and their connection through saliva. We sought to determine whether more tightly defined microhabitats might have more tightly defined sets of resident bacteria. A microhabitat may be characterized, for example, as the space adjacent to a particular species of bacterium. Corncob structures of dental plaque, consisting of coccoid bacteria bound to filaments of Corynebacterium cells, present an opportunity to analyze the community structure of one such well-defined microhabitat within a complex natural biofilm. Here, we investigate by fluorescence in situ hybridization and spectral imaging the composition of the cocci decorating the filaments.ResultsThe range of taxa observed in corncobs was limited to a small subset of the taxa present in dental plaque. Among four major groups of dental plaque streptococci, two were the major constituents of corncobs, including one that was the most abundant Streptococcus species in corncobs despite being relatively rare in dental plaque overall. Images showed both Streptococcus types in corncobs in all individual donors, suggesting that the taxa have different ecological roles or that mechanisms exist for stabilizing the persistence of functionally redundant taxa in the population. Direct taxon-taxon interactions were observed not only between the Streptococcus cells and the central corncob filament but also between Streptococcus cells and the limited subset of other plaque bacteria detected in the corncobs, indicating species ensembles involving these taxa as well.ConclusionsThe spatial organization we observed in corncobs suggests that each of the microbial participants can interact with multiple, albeit limited, potential partners, a feature that may encourage the long-term stability of the community. Additionally, our results suggest the general principle that a precisely defined microhabitat will be inhabited by a small and well-defined set of microbial taxa. Thus, our results are important for understanding the structure and organizing principles of natural biofilms and lay the groundwork for future work to modulate and control biofilms for human health. Video Abstract.

Dataset Information

Crystal structures of barley thioredoxin h isoforms HvTrxh1 and HvTrxh2 reveal features involved in protein recognition and possibly in discriminating the isoform specificity.

Publications

Crystal structures of barley thioredoxin h isoforms HvTrxh1 and HvTrxh2 reveal features involved in protein recognition and possibly in discriminating the isoform specificity.

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