Insight into the orientational versatility of steroid substrates—a docking and molecular dynamics study of a steroid receptor and steroid monooxygenase

Numerous steroids are essential plant, animal, and human hormones. The medical and industrial applications of these hormones require the identification of new synthetic routes, including biotransformations. The metabolic fate of a steroid can be complicated; it may be transformed into a variety of substituted derivatives. This may be because a steroid molecule can adopt several possible orientations in the binding pocket of a receptor or an enzyme. The present study, based on docking and molecular dynamics, shows that it is indeed possible for a steroid molecule to bind to a receptor binding site in two or more orientations (normal, head-to-tail reversed, upside down). Three steroids were considered: progesterone, dehydroepiandrosterone, and 7-oxo-dehydroepiandrosterone. Two proteins were employed as hosts: the human mineralocorticoid receptor and a bacterial Baeyer–Villiger monooxygenase. When the steroids were in nonstandard orientations, the estimated binding strength was found to be only moderately diminished and the network of hydrogen bonds between the steroid and the host was preserved.     

Comparative biochemistry of chondroitin sulphate–proteins of cartilage and notochord

Fragments that consisted mainly of two polysaccharide chains joined by a short polypeptide bridge (doublets) were prepared from chondroitin sulphate-proteins of lamprey, sturgeon, elasmobranch and ox connective tissues after hydrolysis with trypsin and chymotrypsin. Consideration of molecular parameters, compositions and behaviour on gel electrophoresis and density-gradient fractionation leads to a proposed parent structure for chondroitin sulphate-proteins. A single polypeptide chain of about 2000 amino acid residues contains alternating short and long repeating sequences. A short sequence consists of less than 10 amino acid residues with one N-terminal and one C-terminal serine residue, each of which carries a polysaccharide chain linked glycosidically to its hydroxyl group. This structure constitutes the doublet subunit. Some variation is introduced when the doublet subunit carries only a single polysaccharide chain. The long sequence contains about 35 amino acid residues and is subject to cleavage by trypsin and chymotrypsin. The main polypeptide is probably homologous in the vertebrate sub-phylum with strong conservation of structure suggested for the short sequence. However, polymorphism of polypeptide structures cannot be excluded.     

‘Radicle' biochemistry: the biology of root-specific metabolism

The roots of higher plants are a fascinating and largely unexplored biological frontier. One of their features is the ability to synthesize a remarkable diversity of secondary metabolites, and to adjust their metabolic activities in response to biotic and abiotic stress. This includes the ability to exude a complex array of micro- and macromolecules into the rhizosphere, with the potential to affect the inter-relationships between plants and beneficial or deleterious soil-borne organisms. In the past, research on root biology has been hampered by the underground growth habit of roots and by the lack of a suitable experimental system. However, recent progess in growing roots in isolation has greatly facilitated the study of root-specific metabolism and contributed to our understanding of this remarkable plant organ.     

International Congress of the German Mycological Society,University Hamburg,Sept. 16th–23th 2010

Announcement

International Congress of the German Mycological Society, University Hamburg, Sept. 16th–23th 2010