Cyanobacterial hydrogen production

With the global attention and research now being focussed on looking for an alternative to fossil fuel, hydrogen is the hope of future. Cyanobacteria are highly promising microorganisms for biological photohydrogen production. The review highlights the advancement in the biology of cyanobacterial hydrogen production in recent years. It discusses the enzymes involved in hydrogen production, viz. hydrogenases and nitrogenases, various strategies developed by cyanobacteria to limit nitrogenase inactivation by atmospheric and photosynthetic O₂, different biochemical and physicochemical parameters influencing the commercial cyanobacterial hydrogen production and the methods opted by different researchers for eliminating them to obtain maximum and sustained hydrogen production. Integrating the existing knowledge, techniques and expertise available, much future improvement and progress can be made in the field. This revised version was published online in November 2006 with corrections to the Cover Date.     

The ER membrane complex (EMC) can functionally replace the Oxa1 insertase in mitochondria

Two multisubunit protein complexes for membrane protein insertion were recently identified in the endoplasmic reticulum (ER): the guided entry of tail anchor proteins (GET) complex and ER membrane complex (EMC). The structures of both of their hydrophobic core subunits, which are required for the insertion reaction, revealed an overall similarity to the YidC/Oxa1/Alb3 family members found in bacteria, mitochondria, and chloroplasts. This suggests that these membrane insertion machineries all share a common ancestry. To test whether these ER proteins can functionally replace Oxa1 in yeast mitochondria, we generated strains that express mitochondria-targeted Get2–Get1 and Emc6–Emc3 fusion proteins in Oxa1 deletion mutants. Interestingly, the Emc6–Emc3 fusion was able to complement an Δoxa1 mutant and restored its respiratory competence. The Emc6–Emc3 fusion promoted the insertion of the mitochondrially encoded protein Cox2, as well as of nuclear encoded inner membrane proteins, although was not able to facilitate the assembly of the Atp9 ring. Our observations indicate that protein insertion into the ER is functionally conserved to the insertion mechanism in bacteria and mitochondria and adheres to similar topological principles.

Redirecting the core subunits of the protein membrane insertion complex EMC into mitochondria rescues cells deficient for the mitochondrial Oxa1 system; this supports the hypothesis that the machinery for protein insertion into the ER membrane is functionally analogous to the YidC/Oxa1/Alb3 family of bacteria, mitochondria and chloroplasts.     

Modeling breast cancer in vivo and ex vivo reveals an essential role of Pin1 in tumorigenesis

Phosphorylation on certain Ser/Thr-Pro motifs is a major oncogenic mechanism. The conformation and function of phosphorylated Ser/Thr-Pro motifs are further regulated by the prolyl isomerase Pin1. Pin1 is prevalently overexpressed in human cancers and implicated in oncogenesis. However, the role of Pin1 in oncogenesis in vivo is not known. We have shown that Pin1 ablation is highly effective in preventing oncogenic Neu or Ras from inducing cyclin D1 and breast cancer in mice, although it neither affects transgene expression nor mammary gland development. Moreover, we have developed an ex vivo assay to uncover that a significant fraction of primary mammary epithelial cells from Neu or Ras mice display various malignant properties long before they develop tumors in vivo. Importantly, these early transformed properties are effectively suppressed by Pin1 deletion, which can be fully rescued by overexpression of cyclin D1. Thus, Pin1 is essential for tumorigenesis and is an attractive anticancer target. Our ex vivo assay can be used to study early events of breast cancer development in genetically predisposed mice.     

Effect of defolliculation and 17α-hydroxy, 20β-dihydroprogesterone on cyclic AMP level in full-grown oocytes of the rainbow trout,Salmo gairdneri

The changes in cAMP were followed in trout oocytes incubated in vitro after defolliculation performed by either enzymatic or manual dissection. Both defolliculation methods induced a highly significant rise in oocyte cAMP level (4.5 times the basal level of control [follicle-enclosed oocytes], after 6 h). Treatment of defolliculated oocytes with 17α-hydroxy,20β-dihydroprogesterone (17α,20β-OH-P) (10^?6 M), which induced oocyte maturation (germinal vesicle breakdown [GVBD]) was able, first, to interrupt the increase of oocyte cAMP level promoted by defolliculation and then to lower this level significantly down to values that still remained higher than folliculated controls. Very low concentrations of 17α,20β-OH-P (1.38–55.6 10^?9 M), or physiological doses of testosterone (0.35 10^?6 M, in the range found in vivo before ovulation) were able to induce a similar decrease of oocyte cAMP level without inducing GVBD. Under the same experimental conditions estradiol (0.35 10^?6 M) exhibited no action. These results suggest that some factor(s) originating in the follicle (FIF), inhibit the oocytes' tendency to accumulate cAMP before the final surge of 17α,20β-OH-P. This factor might be a follicular steroid such as testosterone or nonmaturing concentrations of 17α,20β-OH-P. Moreover our data favour the hypothesis that the final surge of 17α,20β-OH-P could induce distinct intraoocyte mechanisms: the first induces an irreversible blockage of cAMP level before the inhibitory action of the FIF is suppressed by ovulation, and the second mechanism leads to GVBD.     

Cloning and expression of bovine herpesvirus-1 glycoprotein C

Glycoprotein C (gC) of Bovine Herpesvirus-1 (BHV-1) is expressed at high levels on surface of infected cells and on virus envelope. It is relatively immunodominant in antibody response to BHV-1 infection and protective in immunized bovines against BHV-1 challenge. In an attempt to express gC in mammalian cells, the 2.4 kb BamHI-EcoRI fragment, containing complete coding sequence of the gC gene was excised from a recombinant plasmid and cloned under the control of RSV-LTR. The resultant plasmid pRSV-gC was transfected into MDBK cells and expression of gC was detected by indirect immunofluorescence. The non-permeabilized cells revealed surface expression of gC.     

The LysE superfamily: topology of the lysine exporter LysE of Corynebacterium glutamicum, a paradyme for a novel superfamily of transmembrane solute translocators

In Corynebacterium glutamicum the LysE carrier protein exhibits the unique function of exporting L-lysine. We here analyze the membrane topology of LysE, a protein of 236 amino acyl residues, using PhoA- and LacZ-fusions. The amino-terminal end of LysE is located in the cytoplasm whereas the carboxy-terminal end is found in the periplasm. Although 6 hydrophobic domains were identified based on hydropathy analyses, only five transmembrane spanning helices appear to be present. The additional hydrophobic segment may dip into the membrane or be surface localized. We show that LysE is a member of a family of proteins found, for example, in Escherichia coil, Bacillus subtilis, Mycobacterium tuberculosis and Helicobacter pylori. This family, which we have designated the LysE family, is distantly related to two additional protein families which we have designated the YahN and CadD families. These three families, the members of which exhibit similar sizes, hydropathy profiles, and sequence motifs comprise the LysE superfamily. Functionally characterized members of the LysE superfamily export L-lysine, cadmium and possibly quarternary amines. We suggest that LysE superfamily members will prove to catalyze export of a variety of biologically important solutes.     

Efficacy of human beta-casein fragment (54-59) and its synthetic analogue compound 89/215 against Leishmania donovani in hamsters

The characteristic feature of visceral leishmaniasis (VL) is the profound impairment of immune system of the infected host, which contributes significantly to the partial success of antileishmanial chemotherapy. Since in VL, cure is the combinatorial effect of drug and immune status of the host, the rationale approach towards antileishmanial chemotherapy would be to potentiate the immune functioning of the host to extract desired results. Towards this direction several rationally designed analogues of human beta-casein fragment (54-59) were evaluated for their ability to stimulate the non-specific resistance in hamsters against Leishmania donovani infection. By virtue of being derived from the food protein casein derivatives may be devoid of unwanted side effects associated with the substances of microbial origin, e.g. muramyl dipeptide (MDP). Out of this one peptide Val-Glu-Gly-Ile-Pro-Tyr (compound 89/215) had been reported to have such activity. In this communication, the prophylactic and therapeutic efficacy of the peptide along with its natural sequence has been evaluated in detail against experimental VL in hamsters. Their use as an adjunct to chemotherapy was also explored. Human beta-casein fragment, compound 89/215 and MDP were tested in vivo at various dose levels wherein compound 89/215 showed superiority over MDP at 3 mg/kg x 2 given intraperitoneally (i.p.). Compound 89/215 sensitized peritoneal macrophages acquired considerable resistance and only 24% of the cells were found infected in comparison to control peritoneal macrophages where 76.4% of the cells were found infected. Similarly, the efficacy of sodium antimony gluconate (SAG) in hamsters pretreated with compound 89/215 enhanced significantly (P < 0.001). This peptide also exhibited considerably good therapeutic efficacy when evaluated either alone or in combination with SAG in established infection of L. donovani.     

Clenbuterol induced changes in cholesterol and triglyceride levels of gastrocnemius, pectoralis and heart of rat under work induced stress

Work induced stress led to decreased cholesterol and fluctuating triglyceride levels in gastrocnemius and pectoralis muscles in rats. But the drug (clenbuterol, 2 mg kg(-1) day(-1)) treatment increased cholesterol and triglyceride levels in both the muscles. However, heart showed decreased cholesterol and increased triglyceride level in the animals under work stress, but at the same time drug treatment led to a significant increase in levels of the two lipid fractions, inferring towards deleterious effect of the drug on heart.