ABSTRACT
Biosynthesis of gold nanoparticles by Streptomycetes from Himalayan Mountain was undertaken for the first time. Out of 10 actinomycete strains tested, four strains (D10, HM10, ANS2 and MSU) showed evidence for the intracellular biosynthesis of gold nanoparticles, among which the strain HM10 showed high potency. Presence of spherical and rod shaped gold nanoparticles in mycelium of the strain HM10 was determined by transmission electron microscopy (TEM) and X-ray diffraction analysis. The average particle size ranged from 18-20 nm. UV spectral analysis indicated that the reduction of chloroauric acid (HAuCl4) occurred within 24 h of reaction period. Further, the strain HM10 showed enhanced growth at 1 and 10 mM concentration of HAuCl4. The gold nanoparticles synthesized by the strain HM10 showed good antibacterial activity against S. aureus and E. coli in well-diffusion method. The potential actinomycete HM10 strain was phenotypically characterized and identified as Streptomyces viridogens (HM10). Thus, actinomycete strain HM10 reported in this study is a newly added source for the biosynthesis of gold nanoparticles.
Subject(s)
Actinobacteria/metabolism , Anti-Bacterial Agents/biosynthesis , Anti-Bacterial Agents/chemistry , Chlorides/chemistry , Chlorides/metabolism , Chlorides/pharmacology , Escherichia coli/drug effects , Gold Compounds/chemistry , Gold Compounds/metabolism , Gold Compounds/pharmacology , Microscopy, Electron, Transmission/methods , Nanoparticles/chemistry , Nanotechnology/methods , Staphylococcus aureus/drug effects , Streptomyces/metabolism , X-Ray DiffractionABSTRACT
Antirheumatic gold compounds have been shown to inhibit NF-kB activation by blocking IkB kinase (IKK) activity. To examine the possible inhibitory mechanism of gold compounds, we expressed wild type and mutant forms of IKk alpha and beta subunits in COS-7 cells and determined the effect of gold on the activity of these enzymes both in vivo and in vitro. Substitution of Cys-179 of IKK beta with alanine (C179A) rendered the enzyme to become resistant to inhibition by a gold compound auranofin, however, similar protective effect was not observed with an equivalent level of IKK alpha (C178A) mutant expressed in the cells. Auranofin inhibited constitutively active IKK alpha and beta and variants; IKK alpha (S176E, S180E) or IKK beta (S177E, S181E), suggesting that gold directly cause inhibition of activated enzyme. The different inhibitory effect of auranofin on IKK alpha (C178A) and IKK beta (C179A) mutants indicates that gold could inhibit the two subunits of IKK in a different mode, and the inhibition of NF- kB and IKK activation induced by inflammatory signals in gold-treated cells appears through its interaction with Cys-179 of IKK beta.