A comparative study of the innervation of the choroid plexus in amphibia

The aminergic and cholinergic innervation of choroid plexuses in three species of amphibia was investigated. Plexuses of the Japanese toad and the bullfrog had poor innervation by adrenergic nerves of sympathetic origin, but in the clawed toad, these plexuses were heavily innervated by adrenergic axons from ganglion cells located in the plexus stroma. Nerve fibers positive for acetylcholinesterase were not found in the plexuses, except for a few fibers with very weak enzyme activity in the clawed toad.     

Antimicrobial activity of metal derivatives of sulfonamides

Summary Antimicrobial activities of a series of metal derivatives of some sulfa drugs were examined. Such metal derivatives showed higher antimicrobial activity than the parent sulfa drugs, and among the metals, gold derivatives are seen to be the most effective.We wish to thank for the material supplied by the Central Research Laboratories, Meiji Seika Kaisha, Ltd, for antimicrobial assay.     

Structure of the E. coli signal recognition particle bound to a translating ribosome

The prokaryotic signal recognition particle (SRP) targets membrane proteins into the inner membrane. It binds translating ribosomes and screens the emerging nascent chain for a hydrophobic signal sequence, such as the transmembrane helix of inner membrane proteins. If such a sequence emerges, the SRP binds tightly, allowing the SRP receptor to lock on. This assembly delivers the ribosome-nascent chain complex to the protein translocation machinery in the membrane. Using cryo-electron microscopy and single-particle reconstruction, we obtained a 16 A structure of the Escherichia coli SRP in complex with a translating E. coli ribosome containing a nascent chain with a transmembrane helix anchor. We also obtained structural information on the SRP bound to an empty E. coli ribosome. The latter might share characteristics with a scanning SRP complex, whereas the former represents the next step: the targeting complex ready for receptor binding. High-resolution structures of the bacterial ribosome and of the bacterial SRP components are available, and their fitting explains our electron microscopic density. The structures reveal the regions that are involved in complex formation, provide insight into the conformation of the SRP on the ribosome and indicate the conformational changes that accompany high-affinity SRP binding to ribosome nascent chain complexes upon recognition of the signal sequence.