Alterations of Hair and Nail Content of Selected Trace Elements in Nonoccupationally Exposed Patients with Chronic Depression from Different Geographical Regions

The aim of this study was to determine if altered levels of selected trace elements manifest themselves during chronic depression. To identify elements strongly associated with chronic depression, relationships between the elemental contents of hair and nails and the interelement correlations were checked. Inductively coupled plasma mass spectrometry and ion chromatography were used to evaluate the contents of Zn, Cu, Co, Pb, Mn, and Fe in hair and nail samples from a total of 415 subjects (295 patients and 120 healthy volunteers). The study included logistic regression models to predict the probability of chronic depression. To investigate possible intercorrelations among the studied elements, the scaled principal component analysis was used. The research has revealed differences in TE levels in the group of depressed men and women in comparison to the healthy subjects. Statistically significant differences in both hair and nails contents of several elements were observed. Our study also provides strong evidence that the intermediary metabolism of certain elements is age- and gender-dependent. Zn, Mn, Pb, and Fe contents in hair/nails seem to be strongly associated with chronic depression. We found no statistically significant residence-related differences in the contents of studied elements in nonoccupationally exposed patients and healthy subjects.

Analysis of the regulatory region of the lysC gene of Escherichia coli

A lysC-lac'Z fusion plasmid was constructed to study the regulatory region of the lysC gene. Analysis by deletion mutations confirmed the existence of an alternative promoter, P2, located upstream of the previously identified promoter, P1. The transcription start site of promoter P2 was located 85 base pairs upstream the transcription start site of promoter P1. Both promoters are regulated by lysine.

Molecular structure of kanamycin nucleotidyltransferase determined to 3.0-A resolution

Kanamycin nucleotidyltransferase, as originally isolated from Staphylococcus aureus, inactivates the antibiotic kanamycin by catalyzing the transfer of a nucleotidyl group from nucleoside triphosphates such as ATP to the 4'-hydroxyl group of the aminoglycoside. The molecular structure of the enzyme described here was determined by X-ray crystallographic analysis to a resolution of 3.0 A. Crystals employed in the investigation belonged to the space group P4(3)2(1)2 with unit cell dimensions of a = b = 78.9 A and c = 219.2 A. An electron density map phased with seven heavy-atom derivatives revealed that the molecules packed in the crystalline lattice as dimers exhibiting local 2-fold rotation axes. Subsequent symmetry averaging and solvent flattening improved the quality of the electron density such that it was possible to completely trace the 253 amino acid polypeptide chain. Each monomer is divided into two distinct structural domains: the N-terminal motif composed of residues Met 1-Glu 127 and the C-terminal half delineated by residues Ala 128-Phe 253. The N-terminal region is characterized by a five-stranded mixed beta-pleated sheet whereas the C-terminal domain contains five alpha-helices, four of which form an up-and-down alpha-helical bundle very similar to that observed in cytochrome c'. The two subunits wrap about one another to form an ellipsoid with a pronounced cleft that could easily accommodate the various aminoglycosides known to bind to the enzyme.

Thermostable mutants of kanamycin nucleotidyltransferase are also more stable to proteinase K, urea, detergents, and water-miscible organic solvents

A series of variants of kanamycin nucleotidyltransferase (KNTase), isolated previously on the basis of enhanced thermostability by cloning and selection for enzymatic activity in the thermophile Bacillus stearothermophilus, was used to systematically test the hypothesis that thermostable enzymes would also be more resistant to other forms of protein denaturation. The purified KNTases were treated with proteinase K or assayed at 37 degrees C in the presence of urea, N-lauroylsarcosine, Triton X-100, tetrahydrofuran, ethanol, or dimethylformamide. With all these agents, the KNTases displayed increasing resistance to denaturation in the order: wild type, mutant TK9 (with a Thr130-->Lys substitution), TK1 (Asp80-->Tyr), and TK101 (both substitutions). This is the same order in which their thermostability increases, indicating that the structural mechanism(s) whereby the mutations yield enhanced resistance to heat denaturation also yield stabilization towards chemical forms of enzymatic inactivation. These results suggest that selection in thermophiles is a useful method to obtain enzyme variants with increased overall stability, even at nonthermophilic temperatures.

Crystallization and preliminary crystallographic analysis of a thermostable mutant of kanamycin nucleotidyltransferase

A thermostable mutant of kanamycin nucleotidyltransferase isolated by cloning and selection for kanamycin resistance in Bacillus stearothermophilus at 70 degrees C has been crystallized in a form suitable for high-resolution diffraction analysis. This enzyme catalyzes nucleotidyl group transfer from nucleoside triphosphates such as ATP to hydroxyl groups of various aminoglycosides, thus inactivating the antibiotic. The kanamycin nucleotidyltransferase gene, originally encoded on plasmid pUB110 from the mesophile Staphylococcus aureus, was transferred to the thermophile B. stearothermophilus via shuttle plasmids and the mutant carrying the substitutions D80Y and T130K was isolated from kanamycin-resistant colonies grown at 70 degrees C. The thermostable enzyme was crystallized in two forms from solutions of polyethylene glycol 8000 (PEG8000) using batch and vapor diffusion methods. Type I crystals grown from 19% (w/v) PEG8000 and 200 mM NaCl belong to the orthorhombic space group C222(1), have unit cell dimensions of a = 128.4, b = 156.8, c = 155.8 A, and diffract to at least 2.4-A resolution. The type II form of the crystals were grown from 10% PEG8000, 200 mM KCl, and 3 mM CoCl2, and belong to the tetragonal space group P4(1)2(1)2 or P4(3)2(1)2 with unit cell dimensions of a = b = 78.9, and c = 220.4 A; these crystals diffract to at least 2.5-A resolution.

1,3-Propanediol production by Escherichia coli expressing genes from the Klebsiella pneumoniae dha regulon

The dha regulon in Klebsiella pneumoniae enables the organism to grow anaerobically on glycerol and produce 1,3-propanediol (1,3-PD). Escherichia coli, which does not have a dha system, is unable to grow anaerobically on glycerol without an exogenous electron acceptor and does not produce 1,3-PD. A genomic library of K. pneumoniae ATCC 25955 constructed in E. coli AG1 was enriched for the ability to grow anaerobically on glycerol and dihydroxyacetone and was screened for the production of 1,3-PD. The cosmid pTC1 (42.5 kb total with an 18.2-kb major insert) was isolated from a 1,3-PD-producing strain of E. coli and found to possess enzymatic activities associated with four genes of the dha regulon: glycerol dehydratase (dhaB), 1,3-PD oxidoreductase (dhaT), glycerol dehydrogenase (dhaD), and dihydroxyacetone kinase (dhaK). All four activities were inducible by the presence of glycerol. When E. coli AG1/pTC1 was grown on complex medium plus glycerol, the yield of 1,3-PD from glycerol was 0.46 mol/mol. The major fermentation by-products were formate, acetate, and D-lactate. 1,3-PD is an intermediate in organic synthesis and polymer production. The 1,3-PD fermentation provides a useful model system for studying the interaction of a biochemical pathway in a foreign host and for developing strategies for metabolic pathway engineering.

Effect of temperature on the expression of wild-type and thermostable mutants of kanamycin nucleotidyltransferase in Escherichia coli

The expression of kanamycin nucleotidyltransferase (KNTase) in Escherichia coli results in different forms of the protein, depending on the temperature; soluble active enzyme is synthesized at 23 degrees C but the protein is mostly aggregated and inactive in inclusion bodies when made at 37 degrees C. However, active enzyme can be recovered by solubilization of the inclusion bodies with 8 M urea followed by dilution of the denaturant, indicating that the polypeptide is not damaged covalently but is present in a misfolded state. The availability of thermostable mutants of KNTase allows a test of the hypothesis that formation of inclusion bodies when proteins are highly expressed in E. coli is due to the accumulation of a folding intermediate that is prone to temperature-dependent aggregation. Because these mutants were isolated by cloning the KNTase gene into the thermophile Bacillus stearothermophilus and selecting for kanamycin resistance at high growth temperatures, they must be thermostable for both synthesis and activity and must have folding intermediates that are less susceptible to the formation of aggregates. Indeed, whereas decreasing the temperature from 37 to 23 degrees C increased the KNTase specific activity 10-fold in cells expressing the wild-type enzyme, this change resulted in only a 2.1-fold increase for the TK1 (Asp80----Tyr) mutant and a 1.7-fold increase for the TK101 (Asp80----Tyr and Thr130----Lys) double mutant. The strategy of cloning in thermophiles and selecting or screening for mutants that fold correctly to yield biological activity at high growth temperatures may be useful in overcoming the problem of the insolubility of some proteins when expressed in heterologous hosts.

Quasi-static electric-field-enhanced diffraction effects in a nematic liquid-crystal film

A quasi-static electric field can enhance laser-induced diffraction rings from a nematic liquid-crystal film. This phenomenon is shown to be the combined result of the critical behavior of the sample at the Freedericksz transition and the nonlinear coupling of the optical and quasi-static electric fields.

Adenosine 3',5'-phosphate phosphodiesterase and pheromone response in the yeast Saccharomyces cerevisiae

Theophylline, aminophylline, and isobutylmethylxanthine, compounds reported to be inhibitors of adenosine 3',5'-phosphate (cAMP) phosphodiesterase, prevented the alpha-factor-induced cell cycle arrest of Saccharomyces cerevisiae a cells. To determine whether the in vivo effect of these methylxanthines on yeast pheromone response was related to their known biochemical mode of action, two assays for cAMP phosphodiesterase based on affinity of the product of the reaction (5'-AMP) for boronate groups were developed and were used to monitor the activity of the low Km cAMP phosphodiesterase present in yeast extracts. It was found that the relative efficacy of the methylxanthines as inhibitors of this enzyme in vitro was correlated with the degree to which they antagonized alpha-factor action in vivo. These results were consistent with our previous proposal that pheromone action involves a lowering of cAMP level in the target cell.

Clostridial apoferredoxin messenger ribonucleic acid. Assay and partial purification

An assay for Clostridium pasteurianum apoferredoxin messenger ribonucleic acid (mRNA) was developed, based on the synthesis of the protein in vitro. Quantitation of apoferredoxin synthesis was accomplished by trypsinization of the cell-free incubation labeled with 3H- or 14C-labeled amino acids, separation of the products by SDS-urea polyacrylamide gel electrophoresis, and excising and counting the NCS-solubilized gel band corresponding to the unique 52-amino acid tryptic peptide derived from apoferredoxin. Its synthesis was shown to be RNA dependent, and was optimized with respect to several parameters of the in vitro protein-synthesizing system. The specificity of the assay was examined with RNA from Clostridium acidi urici, a related species the ferredoxin of which does not yield the 52-amino acid tryptic peptide, and by the use of [3H]leucine, which is not present in C. pasteurianum apoferredoxin. By these methods, the overestimation of apoferredoxin synthesis due to the comigration of fragments from other in vitro products with the legitimate apoferredoxin-derived peptide could be accounted for. The apoferredoxin mRNA was partially purified by the sequential zonal sucrose gradient centrifugation of total RNA followed by Sephadex G-200 chromatography of the enriched RNA, after which a fraction was obtained in which apoferredoxin mRNA was 20-fold enriched. The enriched RNA fraction can now be used for further purification of the apoferredoxin-coding sequences by cloning procedures.