Assembly of chloroplast signal recognition particle involves structural rearrangement in cpSRP43

Signal recognition particle in chloroplasts (cpSRP) exhibits the unusual ability to bind and target full-length proteins to the thylakoid membrane. Unlike cytosolic SRPs in prokaryotes and eukaryotes, cpSRP lacks an RNA moiety and functions as a heterodimer composed of a conserved 54-kDa guanosine triphosphatase (cpSRP54) and a unique 43-kDa subunit (cpSRP43). Assembly of the cpSRP heterodimer is a prerequisite for post-translational targeting activities and takes place through interactions between chromatin modifier domain 2 (CD2) of cpSRP43 and a unique 10-amino-acid region in cpSRP54 (cpSRP54_pep). We have used multidimensional NMR spectroscopy and other biophysical methods to examine the assembly and structure of the cpSRP43-cpSRP54 interface. Our data show that CD2 of cpSRP43 binds to cpSRP54_pep in a 1:1 stoichiometry with an apparent K_d of ∼ 1.06 μM. Steady-state fluorescence and far-UV circular dichroism data suggest that the CD2-cpSRP54_pep interaction causes significant conformational changes in both CD2 and the peptide. Comparison of the three-dimensional solution structures of CD2 alone and in complex with cpSRP54_pep shows that significant structural changes are induced in CD2 in order to establish a binding interface contributed mostly by residues in the N-terminal segment of CD2 (Phe5-Val10) and an arginine doublet (Arg536 and Arg537) in the cpSRP54 peptide. Taken together, our results provide new insights into the mechanism of cpSRP assembly and the structural forces that stabilize the functionally critical cpSRP43-cpSRP54 interaction.     

Soybean protein: A natural source for the production of green silver nanoparticles

The ethnopharmacological approach to the production of nanoparticles is directly related to the creation of an important symbiosis between nanoscience and medical science. Production of nanoparticles under ecofriendly conditions is of significance to address growing concerns on the overall toxicity of nanoparticles for medical and biotechnological applications. The present investigation demonstrates silver nanoparticles production capabilities of a miracle bean soybean Glycine max. We found that a single protein of soybean with a molecular weight of 51 kDa stabilizes the newly formed silver nanoparticles. The electroeluted protein has confirmed the bioreduction property of silver ions.     

Photometabolism of Heterocyclic Aromatic Compounds by Rhodopseudomonas palustris OU 11

Rhodopseudomonas palustris OU 11 (ATCC 51186; DSM 7375) isolated from a pond of chemical industry effluent could anaerobically photometabolize heterocyclic aromatic compounds belonging to the pyridine and pyrazine groups only after a period of adaptation on pyrazinoic acid of 5 to 6 weeks. Growth on heterocyclic compounds was light dependent. The effects of various concentrations of heterocyclic compounds on growth suggest that higher concentrations of these compounds inhibit growth and are toxic.     

Effect of pesticides on hydrogen metabolism of Rhodobacter sphaeroides and Rhodopseudomonas palustris

Abstract: The present study reports the effect of 2,4- d , quinalphos, monocrotophos, captan and carbendazim on the hydrogen metabolism (nitrogenase, photoproduction of hydrogen and hydrogenase activities) of two purple non-sulfur bacteria isolated from paddy soils. In general, the pesticides were found to be inhibitory to both nitrogenase and hydrogen photoproduction activities of both the organisms, and their effect on hydrogenase-mediated reactions varied with the pesticides used and the organisms.