Substrate interactions with the alpha-subunit of the Escherichia coli tryptophan synthase. A kinetic study of the wild-type alpha-subunit.

Small-angle X-ray scattering has been used to determine the size and shape of human antithrombin III and its complex with heparin. The scattering data obtained show that antithrombin III behaves like an ellipsoid with semi-axes of 1.9, 3.7, and 5.2 nm. The antithrombin III-heparin complex produces a scattering curve very similar to that of pure antithrombin III, indicating that there is no major change in size and shape upon binding of heparin. The nature of the heparin binding site is discussed.     

Biodehalogenation of low concentrations of 1,3-dichloropropanol by mono- and mixed cultures of bacteria

The degradation of low concentrations of 1,3-dichloro-2-propanol (1,3-DCP) and related halohydrins by whole cells and cell-free extracts of soil bacteria has been investigated. Three bacteria (strains A1, A2, A4), isolated from the same soil sample, were distinguished on the basis of cell morphology, growth kinetics and haloalcohol dehalogenase profiles. Strain A1, probably an Agrobacterium sp., dehalogenated 1,3-DCP with the highest specific activity (0.33 U mg protein⁻¹) and also had the highest affinity for 1,3-DCP (K _m, 0.1 mM). Non-growing cells of this bacterium dehalogenated low concentrations of 1,3-DCP with a first-order rate constant (k ₁) of 1.13 h⁻¹ . The presence of a non-dehalogenating bacterium, strain G1 (tentatively identified as Pseudomonas mesophilius), did not enhance the dehalogenation rate of low 1,3-DCP concentrations. However, the mixed-species consortium of strains A1 and G1 had greater stability than the mono-species culture at DCP concentrations above 1.0 gl⁻¹. Received: 30 April 1996 / Received revision: 30 July 1996 / Accepted: 5 August 1996     

P1, P2'-linked macrocyclic amine derivatives as matrix metalloproteinase inhibitors.

A novel series of 13- and 14-membered macrocyclic amines was developed by linking the P1 and P2' groups. The synthesis entails stereoselective Frater alkylation to install the anti-succinate configuration and macrocyclic amination via nucleophilic displacement. This strategy resulted in a new class of conformationally constrained inhibitors that are potent and selective for MMP-8 and 9 over MMP-1 and 3.     

Slime moulds and the origin of foldback DNA

The genomes of the slime moulds are relatively small when compared with those of higher eukaryotes. They also contain far fewer families of repetitive sequences. Nevertheless, the general patterns of organization of their repetitive DNA are similar. The slime moulds can therefore help us to investigate the structure and evolution of repetitive DNA in “simple” eukaryotes and to understand how these sequences contribute to the architecture and function of the eukaryotic genome. Several questions remain, including perhaps the most important: do repetitive sequences perform some definable function?.