Mechanistic insights into the allosteric regulation of Pseudomonas aeruginosa aspartate kinase.

In plants and microorganisms, aspartate kinase (AK) catalyzes an initial commitment step of the aspartate family amino acid biosynthesis. Owing to various structural organizations, AKs from different species show tremendous diversity and complex allosteric controls. We report the crystal structure of AK from Pseudomonas aeruginosa (PaAK), a typical α2ß2 hetero-tetrameric enzyme, in complex with inhibitory effectors. Distinctive features of PaAK are revealed by structural and biochemical analyses. Essentially, the open conformation of Lys-/Thr-bound PaAK structure clarifies the inhibitory mechanism of α2ß2-type AK. Moreover, the various inhibitory effectors of PaAK have been identified and a general amino acid effector motif of AK family is described.

Over-Expression and Prognostic Significance of FATP5, as a New Biomarker, in Colorectal Carcinoma.

Background: Fatty acid transporters (FATPs) family play an important role in the uptake and metabolism regulation of long-chain fatty acids, which influence the occurrence and developing of multiple tumors. Fatty acid transporter 5(FATP5), a member of FATPs family, participates in fatty acid transport and lipid metabolism and is related to tumor development, whose mechanism in colorectal cancer (CRC) remains unclear. Methods: In this study, we comprehensively utilized a range of relevant bioinformatic tools along with multiple databases to analyze the expression of FATPs family and investigate the biological function and prognostic value of FATP5 in CRC. Besides, cell proliferation and cell cycle distribution analysis, western blotting and immunohistochemistry (IHC) further validated the conclusion of bioinformatics analysis. Results: FATP5 is the only member of FATPs family which was overexpressed in CRC. In the survival analysis based on the GSE39582 databases, the low expression of FATP5 predicts poor prognosis in CRC. Similar results were also observed in GSE17536, GSE28814 and TCGA colon cohorts. The potential function of DNA methylation regulated the abnormal expression of FATP5 in CRC. In addition, enrichment analysis indicated that FATP5 also participates in the regulation of cell cycle. Furthermore, Gene Set Enrichment Analysis (GSEA) showed a strong negative correlation between FATP5 and cell growth, implying that it may participate in regulating cancer cell proliferation by the regulation of cell cycle G2/M transition. At last, we identified that FATP5 was overexpressed in colorectal carcinoma tissues through immunohistochemistry staining, and played an important role in cell cycle by cell proliferation and cell cycle distribution analysis. Conclusion: This study suggested that FATP5 was overexpression in colorectal carcinoma and predicted favorable prognosis, indicating it as a novel appealing prognostic marker for CRC.

Structural and biochemical analysis of 1-Cys peroxiredoxin ScPrx1 from Saccharomyces cerevisiae mitochondria.

BACKGROUND: ScPrx1 is a yeast mitochondrial 1-Cys peroxiredoxins (Prx), a type of Prx enzyme which require thiol-containing reducing agents to resolve its peroxidatic cysteine. ScPrx1 plays important role in protection against oxidative stress. Mitochondrial thioredoxin ScTrx3 and glutathione have been reported to be the physiological electron donor for ScPrx1. However, the mechanism underlying their actions, especially the substrate recognition of ScPrx1 requires additional elucidation. METHODS: The structure of ScPrx1 was obtained through crystallization experiments. The oligomeric state of ScPrx1 was monitored by Blue-Native PAGE. Mutations were generated by the QuikChange PCR-based method. The ScPrx1 activity assay was carried out by measuring the change of 340 nm absorption of the NADPH oxidation. RESULTS: ScPrx1 exist as a homodimer in solution. The structure adopts a typical Prx-fold core which is preceded by an N-terminal ß-hairpin and has a C-terminal extension. Mutations (Glu94Ala, Arg198Ala and Trp126) close to the active site could enhance the catalytic efficiency of ScPrx1 while His83Ala and mutations on α4-ß6 region exhibited reduced activity. The biochemical data also show that the deletion or mutations on ScPrx1 C-terminal have 2-4.56 fold increased activity. CONCLUSION: We inferred that conformational changes of ScPrx1 C-terminal segment were important for its reaction, and the α4-ß6 loop regions around the ScPrx1 active sites were important for the catalytic function of ScPrx1. Collectively, these structural features provides a basis for understanding the diverse reductant species usage in different 1-Cys Prxs.

1,1,3-Trimethyl-3-phenyl-indane.

In the title compound, C(18)H(20), the five-membered ring of the indane fragment adopts an envelope conformation, with the flap atom deviating by 0.399 (3) Šfrom the plane of the remaining four atoms. The dihedral angle between the phenyl ring and the indane benzene ring is 79.58 (7)°.

5-(2-Phenyl-ethyn-yl)isobenzofuran-1,3-dione.

The title compound, C(16)H(8)O(3), was synthesized by the Pd-coupling reaction of phenyl-acetyl-ene with 4-bromo-phthalic anhydride. The phenyl and isobenzofurane rings are nearly coplanar, forming a dihedral angle of 6.70 (10)°. In the crystal structure, centrosymmetrically related mol-ecules are linked into dimers by C-H⋯O hydrogen bonds.