Structure of a NADPH-dependent blue fluorescent protein revealed the unique role of Gly176 on the fluorescence enhancement.

A NADPH-dependent blue fluorescent protein from Vibrio vulnificus CKM-1 (BFPvv) emits blue fluorescence under UV-exposure. Previously, the BFPvvD7 mutant generated by directed evolution displayed a fourfold enhancement in fluorescent intensity. Herein, a further increase in fluorescence in the new BFPvvD8 mutant, with three additional mutations from BFPvvD7, was made. To understand the underlying mechanism of the increased fluorescent intensity of BFPvv, we solved the BFPvvD8-NADPH complex structure. Accompanied with lifetime detection, we proposed that the enhanced intensity is related to the conformational change caused by a glycine residue (Gly176) mutated to other non-glycine residues at a turn close to the NADPH binding site. We also observed the Förster resonance energy transfer (FRET) from our BFPvvD8 to each of the GFP-like fluorescent proteins, mTFP1 and EGFP, joined by an eight-residue linker between the N-terminal of BFPvvD8 and the C-terminal of GFPs. Taken together, with the newly solved BFPvvD8 structure, our results not only provide new considerations within the rational-based protein engineering of this NADPH-dependent BFP, but also suggest that BFPvvD8 could be a potential candidate in FRET-based biosensor techniques.

Protein S-thiolation by Glutathionylspermidine (Gsp): the role of Escherichia coli Gsp synthetASE/amidase in redox regulation.

Certain bacteria synthesize glutathionylspermidine (Gsp), from GSH and spermidine. Escherichia coli Gsp synthetase/amidase (GspSA) catalyzes both the synthesis and hydrolysis of Gsp. Prior to the work reported herein, the physiological role(s) of Gsp or how the two opposing GspSA activities are regulated had not been elucidated. We report that Gsp-modified proteins from E. coli contain mixed disulfides of Gsp and protein thiols, representing a new type of post-translational modification formerly undocumented. The level of these proteins is increased by oxidative stress. We attribute the accumulation of such proteins to the selective inactivation of GspSA amidase activity. X-ray crystallography and a chemical modification study indicated that the catalytic cysteine thiol of the GspSA amidase domain is transiently inactivated by H(2)O(2) oxidation to sulfenic acid, which is stabilized by a very short hydrogen bond with a water molecule. We propose a set of reactions that explains how the levels of Gsp and Gsp S-thiolated proteins are modulated in response to oxidative stress. The hypersensitivities of GspSA and GspSA/glutaredoxin null mutants to H(2)O(2) support the idea that GspSA and glutaredoxin act synergistically to regulate the redox environment of E. coli.

Rare variants discovery by extensive whole-genome sequencing of the Han Chinese population in Taiwan: Applications to cardiovascular medicine.

Introduction: A population-specific genomic reference is important for research and clinical practice, yet it remains unavailable for Han Chinese (HC) in Taiwan. Objectives: We report the first whole genome sequencing (WGS) database of HC (1000 Taiwanese genome (1KTW-WGS)) and demonstrate several applications to cardiovascular medicine. Methods: Whole genomes of 997 HC were sequenced to at least 30X depth. A total of 20,117 relatively healthy HC individuals were genotyped using a customized Axiom GWAS array. We performed a genome-wide genotype imputation technique using IMPUTE2. Results: We identified 26.7 million single-nucleotide variants (SNVs) and 4.2 million insertions-deletions. Of the SNVs, 16.1% were novel relative to dbSNP (build 152), and 34.2% were novel relative to gnomAD. A total of 18,450 healthy HC individuals were genotyped using a customized Genome-Wide Association Study (GWAS) array. We identified hypertension-associated variants and developed a hypertension prediction model based on the correlation between the WGS data and GWAS data (combined clinical and genetic models, AUC 0.887), and also identified 3 novel hyperlipidemia-associated variants. Each individual carried an average of 16.42 (SD = 3.72) disease-causing variants. Additionally, we established an online SCN5A (an important cardiac gene) database that can be used to explore racial differences. Finally, pharmacogenetics studies identified HC population-specific SNVs in genes (CYP2C9 and VKORC1) involved in drug metabolism and blood clotting. Conclusion: This research demonstrates the benefits of constructing a population-specific genomic reference database for precision medicine.

Structure and mechanism of Escherichia coli glutathionylspermidine amidase belonging to the family of cysteine; histidine-dependent amidohydrolases/peptidases.

The bifunctional Escherichia coli glutathionylspermidine synthetase/amidase (GspSA) catalyzes both the synthesis and hydrolysis of Gsp. Its amidase domain (GspA), which catalyzes the hydrolysis of Gsp into glutathione and spermidine, plays an important role in redox sensing and protein S-thiolation. To gain insight of the regulation and catalytic mechanism of and further understand the recycling of the Gsp dimer and Gsp-S-protein adducts, we solved two crystal structures of GspA and GspSA both with the C59A mutation and bound with the substrate, Gsp. In both structures, Cys59, His131, and Glu147 form the catalytic triad, which is similar to other cysteine proteases. Comparison of the GspA_Gsp complex and apo GspSA structures indicates that on binding with Gsp, the side chains of Asn149 and Gln58 of the amidase domain are induced to move closer to the carbonyl oxygen of the cleaved amide bond of Gsp, thereby participating in catalysis. In addition, the helix-loop region of GspA, corresponding to the sequence (30)YSSLDPQEYEDDA(42), involves in regulating the substrate binding. Our previous study indicated that the thiol of Cys59 of GspA is only oxidized to sulfenic acid by H(2)O(2). When comparing the active site of GspA with those of other cysteine proteases, we found that limited space and hydrophobicity of the environment around Cys59 play an important role to inhibit its further oxidation. The structural results presented here not only elucidate the catalytic mechanism and regulation of GspA but also help us to design small molecules to inhibit or probe for the activity of GspA.

Dual binding sites for translocation catalysis by Escherichia coli glutathionylspermidine synthetase.

Most organisms use glutathione to regulate intracellular thiol redox balance and protect against oxidative stress; protozoa, however, utilize trypanothione for this purpose. Trypanothione biosynthesis requires ATP-dependent conjugation of glutathione (GSH) to the two terminal amino groups of spermidine by glutathionylspermidine synthetase (GspS) and trypanothione synthetase (TryS), which are considered as drug targets. GspS catalyzes the penultimate step of the biosynthesis-amide bond formation between spermidine and the glycine carboxylate of GSH. We report herein five crystal structures of Escherichia coli GspS in complex with substrate, product or inhibitor. The C-terminal of GspS belongs to the ATP-grasp superfamily with a similar fold to the human glutathione synthetase. GSH is likely phosphorylated at one of two GSH-binding sites to form an acylphosphate intermediate that then translocates to the other site for subsequent nucleophilic addition of spermidine. We also identify essential amino acids involved in the catalysis. Our results constitute the first structural information on the biochemical features of parasite homologs (including TryS) that underlie their broad specificity for polyamines.