The Mitochondrial tRNAPhe 625G>A Mutation in Three Han Chinese Families With Cholecystolithiasis.

In this study, we assessed three Chinese families with inherited cholecystolithiasis and conducted the clinical, genetic, and molecular characterization of these subjects. Eight of eighteen matrilineal relatives had a clinical phenotype in these three families. Sequence analysis of complete mitochondrial genomes in these probands identified the homoplasmic tRNAPhe 625 G > A mutation and distinct sets of mtDNA polymorphisms belonging to haplogroups H2, F4b, and M10a. The 625G > A mutation disturbed the classic G-C base-pairings at a highly conserved position 49 in the T-stem of mitochondrial tRNAs. Molecular dynamics simulation showed that the structure of tRNAphe with 625 G > A mutation was noticeably remodeled while compared with the isoform of the wild type. The occurrence of tRNAPhe 625 G > A mutation in these various genetically unrelated subjects strongly indicates that this mutation is involved in the pathogenesis of cholecystolithiasis. This is the first evidence that tRNA mutations are associated with cholecystolithiasis, and it provided more insights into the genetic mechanism of cholecystolithiasis.

Leber's hereditary optic neuropathy-associated ND6 14484T > C mutation caused pleiotropic effects on the complex I, RNA homeostasis, apoptosis and mitophagy.

Leber's hereditary optic neuropathy (LHON) is a maternally inherited eye disease due to mitochondrial DNA (mtDNA) mutations. LHON-linked ND6 14484T > C (p.M64V) mutation affected structural components of complex I but its pathophysiology is poorly understood. The structural analysis of complex I revealed that the M64 forms a nonpolar interaction Y59 in the ND6, Y59 in the ND6 interacts with E34 of ND4L, and L60 of ND6 interacts with the Y114 of ND1. These suggested that the m.14484T > C mutation may perturb the structure and function of complex I. Mutant cybrids constructed by transferring mitochondria from lymphoblastoid cell lines of one Chinese LHON family into mtDNA-less (ρo) cells revealed decreases in the levels of ND6, ND1 and ND4L. The m.14484T > C mutation may affect mitochondrial mRNA homeostasis, supported by reduced levels of SLIRP and SUPV3L1 involved in mRNA degradation and increasing expression of ND6, ND1 and ND4L genes. These alterations yielded decreased activity of complex I, respiratory deficiency, diminished mitochondrial ATP production and reduced membrane potential, and increased production of reactive oxygen species in the mutant cybrids. Furthermore, the m.14484T > C mutation promoted apoptosis, evidenced by elevating Annexin V-positive cells, release of cytochrome c into cytosol, levels in apoptotic proteins BAX, caspases 3, 7, 9 and decreasing levels in anti-apoptotic protein Bcl-xL in the mutant cybrids. Moreover, the cybrids bearing the m.14484T > C mutation exhibited the reduced levels of autophagy protein LC3, increased levels of substrate P62 and impaired PINK1/Parkin-dependent mitophagy. Our findings highlighted the critical role of m.14484T > C mutation in the pathogenesis of LHON.

Crystal and solution structures of a novel antimicrobial peptide from Chrysomya megacephala.

Antimicrobial peptides (AMPs) are small amphipathic peptides that exhibit bactericidal activity against a wide range of pathogenic microorganisms and are considered to be potential substitutes for antibiotics effective against microbial infection. PSK, an 84-amino-acid AMP recently isolated from Chrysomya megacephala larvae, probably belongs to the mitochondrial ATPase inhibitor family according to its sequence. No member of this family from an insect has been structurally characterized to date. In this study, the crystal structure of full-length PSK determined by molecular replacement using an ab initio modeled ensemble as a search model and a solution structure obtained from small-angle X-ray scattering (SAXS) measurements are reported. The crystal structure reveals a distinct fold compared with those of homologous peptides, in that PSK comprises two antiparallel α-helices rather than a single long helix, which is in good agreement with the SAXS-based ab initio model. However, the peptide exists as a monomer in solution, even though a stable dimer was observed in the crystal structure. This apparent contradiction may reflect different oligomerization states that may be implicated in its bioactivity. The data presented here have established a solid basis for further mechanistic studies of this novel insect AMP.

Mechanistic insights into mitochondrial tRNAAla 3'-end metabolism deficiency.

Mitochondrial tRNA 3'-end metabolism is critical for the formation of functional tRNAs. Deficient mitochondrial tRNA 3'-end metabolism is linked to an array of human diseases, including optic neuropathy, but their pathophysiology remains poorly understood. In this report, we investigated the molecular mechanism underlying the Leber's hereditary optic neuropathy (LHON)-associated tRNAAla 5587A>G mutation, which changes a highly conserved adenosine at position 73 (A73) to guanine (G73) on the 3'-end of the tRNA acceptor stem. The m.5587A>G mutation was identified in three Han Chinese families with suggested maternal inheritance of LHON. We hypothesized that the m.5587A>G mutation altered tRNAAla 3'-end metabolism and mitochondrial function. In vitro processing experiments showed that the m.5587A>G mutation impaired the 3'-end processing of tRNAAla precursors by RNase Z and inhibited the addition of CCA by tRNA nucleotidyltransferase (TRNT1). Northern blot analysis revealed that the m.5587A>G mutation perturbed tRNAAla aminoacylation, as evidenced by decreased efficiency of aminoacylation and faster electrophoretic mobility of mutated tRNAAla in these cells. The impact of m.5587A>G mutation on tRNAAla function was further supported by increased melting temperature, conformational changes, and reduced levels of this tRNA. Failures in tRNAAla metabolism impaired mitochondrial translation, perturbed assembly and activity of oxidative phosphorylation complexes, diminished ATP production and membrane potential, and increased production of reactive oxygen species. These pleiotropic defects elevated apoptotic cell death and promoted mitophagy in cells carrying the m.5587A>G mutation, thereby contributing to visual impairment. Our findings may provide new insights into the pathophysiology of LHON arising from mitochondrial tRNA 3'-end metabolism deficiency.

Synthesis of Flavonols via Pyrrolidine Catalysis: Origins of the Selectivity for Flavonol versus Aurone.

A novel synthetic method for flavonol from 2'-hydroxyl acetophenone and benzaldehyde promoted by pyrrolidine under an aerobic condition in water is established. This protocol was supported by efficient synthesis of 44 common examples and three natural products. The α, ß-unsaturated iminium ion (enimine ion E) was proved to be the key intermediate in the reaction. H218O and 18O2 isotope tracking experiments demonstrated that both water and the aerobic atmosphere were necessary to ensure the transformation. The selectivity for flavonol or aurone was originated from solvent-triggered intermediates, which were determined by UV-visible spectra from isolated enimine. The phenol-iminium E-A is dominant in water and the ketoenamine intermediate E-B is prevalent in acetonitrile. In the presence of pyrrolidine and oxygen, E-A leads to flavonol through E-I, a zwitterionic-like phenoloxyl-iminium ion, following the key steps of cyclization and a [2 + 2] oxidation; E-B proceeds through path II, a radical process induced by photolysis of E-B with both pyrrolidine and oxygen, to afford aurone. Preliminary mechanistic studies are reported.

CsSbF2 SO4 : An Excellent Ultraviolet Nonlinear Optical Sulfate with a KTiOPO4 (KTP)-type Structure.

A novel noncentrosymmetric (NCS) polar fluoride sulfate, CsSbF2 SO4 , was obtained by ionothermal synthesis. A meticulously designed co-substitution approach was used to successfully replace the [TiO6 ]8- and [PO4 ]3- functional groups in KTiOPO4 (KTP) with [SbO4 F2 ]7- and [SO4 ]2- units, respectively. The structure of CsSbF2 SO4 features a pseudo-3D framework consisting of interconnected 1D [SbF2 O2 SO4 ]5- chains of corner-sharing [SbO4 F2 ]7- octahedra and [SO4 ]2- tetrahedra. The title compound exhibits a sharply enlarged band gap compared to its parent compound, KTP, benefitting from the introduction of F- ions and the displacement of Sb3+ cations. Second harmonic generation (SHG) measurements manifested that CsSbF2 SO4 is phase-matchable and revealed a strong SHG response of about 3.0 KH2 PO4 (KDP), which is the highest value reported for any metal sulfate reported to date. The reported fluoride sulfate is a promising near ultraviolet (UV) nonlinear optical (NLO) material.

Cation-tuned synthesis of the A2SO4·SbF3 (A = Na+, NH4+, K+, Rb+) family with nonlinear optical properties.

Four antimony fluoride sulfates named A2SO4·SbF3 (A = Na+, NH4+, K+, Rb+) have been successfully synthesized using a hydrothermal method by introducing Sb3+ cations with a stereochemically active lone pair in sulfates and subsequently tuning the structure through the second monovalent cations. All of the title compounds are stoichiometrically equivalent materials which share a common structural motif composed of a distorted SO4 tetrahedron and an asymmetric SbF3 polyhedron. However, the macroscopic centricities of these four compounds are significantly influenced by the size and coordination environment of cations; Na2SO4·SbF3 crystallizes in centrosymmetric space groups Cmca and (NH4)2SO4·SbF3 in Pbca, while K2SO4·SbF3 and Rb2SO4·SbF3 crystallizes in noncentrosymmetric space group P212121. Complete characterization including thermal analyses, infrared and UV-vis spectroscopy, and theoretical calculations is also reported. Powder second harmonic generation measurement for noncentrosymmetric K2SO4·SbF3 and Rb2SO4·SbF3 indicated that both of them are type I phase-matchable.