Differential expression of enzyme activities initiating anoxic metabolism of various aromatic compounds via benzoyl-CoA

The regulation of the expression of enzyme activities catalyzing initial reactions in the anoxic metabolism of various aromatic compounds was studied at the whole cell level in the denitrifying Pseudomonas strain K 172. The specific enzyme activities were determined after growth on six different aromatic substrates (phenol, 4-hydroxybenzoate, benzoate, p-cresol, phenylacetate, 4-hydroxyphenylacetate) all being proposed to be metabolized anaerobically via benzoyl-CoA. As a control cells were grown on acetate, or aerobically on benzoate. The expression of the following enzyme activities was determined.Phenol carboxylase, as studied by the isotope exchange between ¹⁴CO₂ and the carboxyl group of 4-hydroxybenzoate; 4-hydroxybenzoyl-CoA reductase (dehydroxylating); p-cresol methylhydroxylase; 4-hydroxybenzyl alcohol dehydrogenase; 4-hydroxybenzaldehyde dehydrogenase; coenzymeA ligases for the aromatic acids benzoate, 4-hydroxybenzoate, phenylacetate, and 4-hydroxyphenylacetate; phenylglyoxylate: acceptor oxidoreductase and 4-hydroxyphenylglyoxylate: acceptor oxidoreductase; aromatic alcohol and aldehyde dehydrogenases.The formation of most active enzymes is strictly regulated; they were only induced when required, the basic activities being almost zero. The observed whole cell regulation pattern supports the postulate that the enzyme activities play a role in anoxic aromatic metabolism and that the compounds are degraded via the following intermediates: Phenol 4-hydroxybenzoate 4-hydroxybenzoyl-CoA benzoyl-CoA; 4-hydroxybenzoate 4-hydroxybenzoyl-CoA benzoyl-CoA; benzoate benzoyl-CoA; p-cresol 4-hydroxybenzaldehyde 4-hydroxybenzoate 4-hydroxybenzoyl-CoA benzoyl-CoA; phenylacetate phenylacetyl-CoA phenylglyoxylate benzoyl-CoA plus CO₂; 4-hydroxyphenylacetate 4-hydroxyphenylacetyl-CoA 4-hydroxyphenylglyoxylate 4-hydroxybenzoyl-CoA plus CO₂ benzoyl-CoA.     

ON THE REVERSIBILITY OF MANDIBULAR SYMPHYSEAL FUSION

Experimental and comparative studies suggest that a major determinant of increased ossification of the mandibular symphysis is elevated masticatory stress related to a mechanically challenging diet. However, the morphology of this joint tracks variation in dietary properties in only some mammalian clades. Extant anthropoid primates are a notable exception: synostosis is ubiquitous in this speciose group, despite its great age and diverse array of feeding adaptations. One possible explanation for this pattern is that, once synostosis evolves, reversion to a lesser degree of fusion is unlikely or even constrained. If correct, this has important implications for functional and phylogenetic analyses of the mammalian feeding apparatus. To test this hypothesis, we generated a molecular tree for 76 vespertilionoid and noctilionoid chiropterans using Bayesian phylogenetic analysis and examined character evolution using parsimony and likelihood ancestral-state reconstructions along with the binary state speciation and extinction (BiSSE) model. Results indicate that reversals have occurred within Vespertilionoidea. In contrast, noctilionoids exhibit an anthropoid-like pattern, which suggests that more detailed comparisons of the functional and developmental bases for fusion in these bat clades may provide insight into why fusion is maintained in some lineages but not in others. Potential functional and developmental explanations for the lack of reversal are discussed.     

Molecular phylogenetics reveals Leontodon (Asteraceae, Lactuceae) to be diphyletic

The plastid matK gene, trnL/F spacer, and nuclear rDNA ITS were sequenced for 36 species of Leontodon and 29 taxa of related genera of tribe Lactuceae. Phylogenetic relationships inferred from the independent and combined data are largely congruent and reveal that Leontodon sensu lato (s.l.) as presently defined is diphyletic: L. subgenus Leontodon forms a clade with Helminthotheca, Picris and Hypochaeris as sister genera, whereas L. subgenus Oporinia appears as a separate clade with strong bootstrap support and is thus better treated as a separate genus. Previous sectional classifications of Leontodon s.l. are considered in the light of DNA and additional morphological and karyological data. Support is presented for a core group of Hypochaeridinae sensu stricto (s.s.) with the two clades of Leontodon s.l., Helminthotheca, Picris, and Hypochaeris, whereas Urospermum, Hyoseris, Aposeris, and Rhagadiolus appear to be positioned more distantly.     

The effects of a 30-min nap during night shift following a prophylactic sleep in the afternoon

Sleep and Biological Rhythms - The purpose of this study was to investigate the effects of a 30-min nap, during a simulated night shift environment, when a prophylactic daytime sleep was...     

Relationship between dim light melatonin onset and the timing of sleep in sleep onset insomniacs

Sleep and Biological Rhythms - Dim light melatonin onset (DLMO), a phase marker of the circadian system can be estimated from sleep diaries of good sleepers. Previous studies have shown a strong...     

Solution structure of the third TB domain from LTBP1 provides insight into assembly of the large latent complex that sequesters latent TGF-beta

Almost all TGF-beta is secreted as part of a large latent complex. This complex is formed from three molecules, a latent transforming growth factor-beta binding protein (LTBP), which plays roles in targeting and activation, a latency associated peptide (LAP), which regulates latency, and the TGF-beta cytokine. LAP is the TGF-beta pro-peptide that is cleaved intracellularly prior to secretion, and TGF-beta binds non-covalently to LAP. Formation of the large latent complex is important for the efficient secretion of TGF-beta. Previous studies have revealed that the LTBP-LAP interaction is mediated by intracellular exchange of a single disulphide bond within the third, and only the third, TB domain (TB3) with LAP. We have previously reported the structure of a homologous TB domain from fibrillin-1. However, TB3 contains a two amino acid insertion, not found in fibrillin-1 TB domains, which is not amenable to molecular modelling. In order to clarify the basis of TB domain function, we have determined the solution NMR structure of TB3(LTBP1). Comparison with the fibrillin-1 TB domain reveals that the two-residue insertion is associated with a significant increase in solvent accessibility of one of the disulphide bonds (linking the second and sixth cysteine residues). Site-directed mutagenesis and NMR studies indicate that this is the only disulphide bond that can be removed without perturbing the TB domain fold. Furthermore, a ring of negatively charged residues has been identified that surrounds this disulphide bond. Homology modelling suggests that the surface properties of TB3 domains from different LTBP isoforms correlate with binding activities. This research provides testable hypotheses regarding the molecular basis of complex formation between LTBPs and LAPs.