Role of transmembrane segment 5 of the plant vacuolar H+-pyrophosphatase

Vacuolar H+-translocating inorganic pyrophosphatase (V-PPase; EC 3.6.1.1) is a homodimeric proton translocase consisting of a single type of polypeptide with a molecular mass of approximately 81 kDa. Topological analysis tentatively predicts that mung bean V-PPase contains 14 transmembrane domains. Alignment analysis of V-PPase demonstrated that the transmembrane domain 5 (TM5) of the enzyme is highly conserved in plants and located at the N-terminal side of the putative substrate-binding loop. The hydropathic analysis of V-PPase showed a relatively lower degree of hydrophobicity in the TM5 region as compared to other domains. Accordingly, it appears that TM5 is probably involved in the proton translocation of V-PPase. In this study, we used site-directed mutagenesis to examine the functional role of amino acid residues in TM5 of V-PPase. A series of mutants singly replaced by alanine residues along TM5 were constructed and over-expressed in Saccharomyces cerevisiae; they were then used to determine their enzymatic activities and proton translocations. Our results indicate that several mutants displayed minor variations in enzymatic properties, while others including those mutated at E225, a GYG motif (residues from 229 to 231), A238, and R242, showed a serious decline in enzymatic activity, proton translocation, and coupling efficiency of V-PPase. Moreover, the mutation at Y230 relieved several cation effects on the V-PPase. The GYG motif presumably plays a significant role in maintaining structure and function of V-PPase.     

Def1p is involved in telomere maintenance in budding yeast

Saccharomyces Rrm3p, a member of Pif1 5'-3' DNA helicase subfamily, helps replication forks traverse protein-DNA complexes, including the telomere. Here we have identified an Rrm3p interaction protein known to be Def1p. In def1 mutants, telomeres were approximately 200-bp shorter than that in wild-type cells. DEF1 is also required for the stable maintenance of mitochondrial DNA, and the telomere shortening phenotype seen in def1 cells is not a secondary consequence of the mitochondrion defect. A combination of DEF1 null mutation with deletion of EST2 or EST3 resulted in an accelerated senescence phenotype, suggesting that Def1p is not involved in the telomerase recruitment pathway. In the absence of telomerase, cells escape senescence by either amplifying Y' regions or TG-telomeric repeats to generate type I or type II survivors, respectively. Only type I survivors were recovered from both def1Delta est2Delta and def1Delta est3Delta double mutant cells, further suggesting that the function of Def1p in telomere maintenance is specific. Our novel findings of the functions of Def1p in telomere and mitochondria suggested that Def1p plays multiple roles in yeast.     

Genetic mapping and comparative analysis of seven mutants related to seed fiber development in cotton

Mapping of genes that play major roles in cotton fiber development is an important step toward their cloning and manipulation, and provides a test of their relationships (if any) to agriculturally-important QTLs. Seven previously identified fiber mutants, four dominant (Li ₁, Li ₂, N ₁ and Fbl) and three recessive (n ₂, sma-4(h _a), and sma-4(fz)), were genetically mapped in six F₂ populations comprising 124 or more plants each. For those mutants previously assigned to chromosomes by using aneuploids or by linkage to other morphological markers, all map locations were concordant except n ₂, which mapped to the homoeolog of the chromosome previously reported. Three mutations with primary effects on fuzz fibers (N ₁, Fbl, n ₂) mapped near the likelihood peaks for QTLs that affected lint fiber productivity in the same populations, perhaps suggesting pleiotropic effects on both fiber types. However, only Li ₁ mapped within the likelihood interval for 191 previously detected lint fiber QTLs discovered in non-mutant crosses, suggesting that these mutations may occur in genes that played early roles in cotton fiber evolution, and for which new allelic variants are quickly eliminated from improved germplasm. A close positional association between sma-4(h _a ), two leaf and stem-borne trichome mutants (t ₁ , t ₂), and a gene previously implicated in fiber development, sucrose synthase, raises questions about the possibility that these genes may be functionally related. Increasing knowledge of the correspondence of the cotton and Arabidopsis genomes provides several avenues by which genetic dissection of cotton fiber development may be accelerated.     

Decrease of CD4+ T-lymphocytes in children exposed to environmental lead

The effects of environmental lead on the immune system of young children were assessed by determining the peripheral blood lymphocytes CD3⁺, CD4⁺, CD8⁺, B(CD19⁺) counts, and natural killer (CD16⁺ CD56⁺) cells in 35 preschool children whose mean blood lead level was 140.6 μg/L. The results were compared to an age- and sex-matched control group with a mean blood lead level of 64.3 μg/L. Compared to the controls, a significant reduction in the percentage of CD4⁺ cells and a significant increase of CD8⁺ cells were seen in the high-lead group. The negative correlation between the percentage of CD4⁺ cells and blood lead levels was found to be significant (p<0.01). These results suggest that exposure to environmental lead might result in alterations in the immune function of young children.     

Design, synthesis, and evaluation of 2-phenoxy-indan-1-one derivatives as acetylcholinesterase inhibitors

A series of 2-phenoxy-indan-1-one derivatives have been designed, synthesized, and tested as acetylcholinesterase inhibitors. The most potent compound exhibited high AChE inhibitory activity (IC50 = 50 nM), and the molecular docking study indicated that it was nicely accommodated by AChE.     

On the role of E-ring oxygen atoms in the binding of camptothecin to the topoisomerase I-DNA covalent binary complex

A recent X-ray crystallographic analysis of the binding of a water soluble camptothecin analogue to the human topoisomerase I-DNA covalent binary complex has suggested the existence of some novel features in the way that camptothecin is bound to the binary complex. Four additional models based on chemical and biochemical data have also been proposed. Presently we describe S-containing analogues of camptothecin prepared on the basis of these models, and report their ability to form stable ternary complexes with human topoisomerase I, and to mediate cytotoxicity at the locus of topoisomerase I. The results indicate that replacement of the 20-OH group of CPT with a SH functionality results in diminution of the potency of CPT as a topoisomerase I poison, while replacement of the O atoms at positions 20 and 21 with S atoms results in essentially complete loss of topoisomerase I inhibitory activity.     

Snapshot of HIV pathogenesis in China

Several reviews have focused on the nature of HIV infection and its spread in various geographical regions of China. In contrast, this review provides a comprehensive update on the prevalence of multiple HIV-1 subtypes, consequent emergence of recombinant and novel forms of HIV-1 in China, and the implications this may have on HIV diversity and the development of effective vaccines. In addition it also examines the dissemination of primary drug resistance in therapy na?ve patients, as well as co-infections with two other important viruses-hepatitis B and C. The main purpose of this review is to provide a current snapshot of HIV-1 pathogenesis in China and possibly shed some light on the future of HIV evolution, and potential challenges for future vaccine and anti-retroviral therapeutics against HIV strains in this area.     

The human plasma proteome: analysis of Chinese serum using shotgun strategy

We have investigated the serum proteome of Han-nationality Chinese by using shotgun strategy. A complete proteomics analysis was performed on two reference specimens from a total of 20 healthy donors, in which each sample was made from ten-pooled male or female serum, respectively. The methodology used encompassed (1) removal of six high-abundant proteins; (2) tryptic digestion of low- and high-abundant proteins of serum; (3) separation of peptide mixture by RP-HPLC followed by ESI-MS/MS identification. A total of 944 nonredundant proteins were identified under a stringent filter condition (X(corr) > or = 1.9, > or = 2.2, and > or = 3.75, < or = C(n) > or = 0.1, and R(sp) > or = 4.0) in both pooled male and female samples, in which 594 and 622 entire proteins were found, respectively. Compared with the total 3020 protein identifications confirmed by more than one laboratory or more than one specimen in HUPO Plasma Proteome Project (PPP) participating laboratories recently, 206 proteins were identified with at least two distinct peptides per protein and 185 proteins were considered as high-confidence identification. Moreover, some lower abundance serum proteins (ng/mL range) were detected, such as complement C5 and CA125, routinely used as an ovarian cancer marker in plasma and serum. The resulting nonredundant list of serum proteins would add significant information to the knowledge base of human plasma proteome and facilitate disease markers discovery.