Structure of yeast sulfhydryl oxidase erv1 reveals electron transfer of the disulfide relay system in the mitochondrial intermembrane space.

The disulfide relay system in the mitochondrial intermembrane space drives the import of proteins with twin CX(9)C or twin CX(3)C motifs by an oxidative folding mechanism. This process requires disulfide bond transfer from oxidized Mia40 to a substrate protein. Reduced Mia40 is reoxidized/regenerated by the FAD-linked sulfhydryl oxidase Erv1 (EC 1.8.3.2). Full-length Erv1 consists of a flexible N-terminal shuttle domain (NTD) and a conserved C-terminal core domain (CTD). Here, we present crystal structures at 2.0 Å resolution of the CTD and at 3.0 Å resolution of a C30S/C133S double mutant of full-length Erv1 (Erv1FL). Similar to previous homologous structures, the CTD exists as a homodimer, with each subunit consisting of a conserved four-helix bundle that accommodates the isoalloxazine ring of FAD and an additional single-turn helix. The structure of Erv1FL enabled us to identify, for the first time, the three-dimensional structure of the Erv1NTD, which is an amphipathic helix flanked by two flexible loops. This structure also represents an intermediate state of electron transfer from the NTD to the CTD of another subunit. Comparative structural analysis revealed that the four-helix bundle of the CTD forms a wide platform for the electron donor NTD. Moreover, computational simulation combined with multiple-sequence alignment suggested that the amphipathic helix close to the shuttle redox enter is critical for the recognition of Mia40, the upstream electron donor. These findings provide structural insights into electron transfer from Mia40 via the shuttle domain of one subunit of Erv1 to the CTD of another Erv1 subunit.

Structures of Saccharomyces cerevisiae D-arabinose dehydrogenase Ara1 and its complex with NADPH: implications for cofactor-assisted substrate recognition.

The primary role of yeast Ara1, previously mis-annotated as a D-arabinose dehydrogenase, is to catalyze the reduction of a variety of toxic α,ß-dicarbonyl compounds using NADPH as a cofactor at physiological pH levels. Here, crystal structures of Ara1 in apo and NADPH-complexed forms are presented at 2.10 and 2.00 Šresolution, respectively. Ara1 exists as a homodimer, each subunit of which adopts an (α/ß)8-barrel structure and has a highly conserved cofactor-binding pocket. Structural comparison revealed that induced fit upon NADPH binding yielded an intact active-site pocket that recognizes the substrate. Moreover, the crystal structures combined with computational simulation defined an open substrate-binding site to accommodate various substrates that possess a dicarbonyl group.

Structural insights into the cofactor-assisted substrate recognition of yeast quinone oxidoreductase Zta1.

Quinone oxidoreductase (QOR EC1.6.5.5) catalyzes the reduction of quinone to hydroxyquinone using NADPH as a cofactor. Here we present the crystal structure of the ζ-crystallin-like QOR Zta1 from Saccharomycescerevisiae in apo-form at 2.00 Šand complexed with NADPH at 1.59 Šresolution. Zta1 forms a homodimer, with each subunit containing a catalytic and a cofactor-binding domain. Upon NADPH binding to the interdomain cleft, the two domains shift towards each other, producing a better fit for NADPH, and tightening substrate binding. Computational simulation combined with site-directed mutagenesis and enzymatic activity analysis defined a potential quinone-binding site that determines the stringent substrate specificity. Moreover, multiple-sequence alignment and kinetics assays implied that a single-residue change from Arg in lower organisms to Gly in vertebrates possibly resulted in elevation of enzymatic activity of ζ-crystallin-like QORs throughout evolution.

Effective-constituent compatibility-based analysis of Bufei Yishen formula, a traditional herbal compound as an effective treatment for chronic obstructive pulmonary disease.

OBJECTIVE: Critical effective constituents were identified from Bufei Yishen formula (BYF), a traditional herbal compound and combined as effective-constituent compatibility (ECC) of BYF I, which may have potential bioactive equivalence to BYF. METHODS: The active constituents of BYF were identified using four cellular models and categorised into Groups 1 (Bufeiqi), 2 (Bushen), 3 (Huatan) and 4 (Huoxue) according to Chinese medicinal theory. An orthogonal design and a combination method were used to determine the optimal ratios of effective constituents in each group and the ratios of "Groups 1 to 4" according to their pharmacological activity. We also comprehensively assessed bioactive equivalence between the BYF and the ECC of BYF I in a rat model of chronic obstructive pulmonary disease (COPD). RESULTS: We identified 12 active constituents in BYF. The numbers of constituents in Groups 1 to 4 were 3, 2, 5 and 2, respectively. We identified the optimal ratios of effective constituents within each group. In Group 1, total ginsenosides:Astragalus polysaccharide:astragaloside IV ratio was 9:5:2. In Group 2, icariin:schisandrin B ratio was 100:12.5. In Group 3, nobiletin:hesperidin:peimine:peiminine:kaempferol ratio was 4:30:6.25:0:0. In Group 4, paeoniflorin:paeonol ratio was 4:1. An orthogonal design was then used to establish the optimal ratios of Group 1, Group 2, Group 3 and Group 4 in ECC of BYF I. The ratio for total ginsenosides:Astragalus polysaccharide:astragaloside IV:icariin:schisandrin B:nobiletin:hesperidin:peimine:paeoniflorin:paeonol was determined to be 22.5:12.5:5:100:12.5:4:30:6.25:25:6.25. A comprehensive evaluation confirmed that ECC of BYF I presented with bioactive equivalence to the original BYF. CONCLUSION: Based on the ECC of traditional Chinese medicine formula method, the effective constituents of BYF were identified and combined in a fixed ratio as ECC of BYF I that was as effective as BYF itself in treating rats with COPD.