Towards understanding the glycoprotein hormone receptors.

Lutropin (LH), follitropin (FSH) and thyrotropin (TSH), as well as choriogonadotropin (CG, which binds to the LH receptor) constitute the glycoprotein hormone family. Their 3 receptors have been cloned during the last few months. They belong to the large group of G-protein coupled membrane proteins, with their specific N-terminal domain likely to bind the hormone and the characteristic 7 membrane-spanning segments in their C-terminal moiety. The present review discusses the main results of amino acid sequence analysis performed on the glycoprotein hormone receptors. The putative extracellular head exhibits less than 45% homology over the 3 receptors, while approximately 70% residue conservation is found in the transmembrane moiety. Here only, limited sequence homologies (approximately 20%) can be found with other G-protein coupled receptors. The secondary structure predictions performed on the 3 receptors revealed that the polypeptide sequence predicted as ordered (either alpha-helix or beta-strand) were repeated evenly throughout the extracellular head with a period of approximately 25 amino acids. This analysis helped to define the intervening loops between this ordered stretches as potential candidates for bearing at least part of the binding site of the hormones. Some of the perspectives opened by the cloning of the receptors are described, like the production of the extracellular head of the porcine LH receptor in baculovirus-infected insect cells, and the exploration of the LH receptor's mechanism of functioning as a dimer.     

Metabolic removal of phosphate from sewage effluent

Eutrophication, or fertilization, has become a major water pollution problem associated with the discharge of mineral-rich sewage eflluent. A metabolic process to remove dissolved phosphate from sewage through the action of sewage microorganisms is under development. The process, unlike other proposed solutions to the problem, would not require tertiary treatment of the sewage. Laboratory studies have produced promising data. Early reports from municipal sewage treatment plants confirm the expectation that the process may be feasible for widespread use.     

Labeled release — An experiment in radiorespirometry

The Labeled Release extraterrestrial life detection experiment onboard the Viking spacecraft is described as it will be implemented on the surface of Mars in 1976. This experiment is designed to detect heterotrophic life by supplying a dilute solution of radioactive organic substrates to a sample of Martian soil and monitoring for evolution of radioactive gas. A significantly attenuated response by a heat-sterilized control sample of the same soil would confirm a positive metabolic response. Experimental assumptions as well as criteria for the selection of organic substrates are presented. The Labeled Release nutrient has been widely tested, is versatile in eliciting terrestrial metabolic responses, and is stable to heat sterilization and to the long-term storage required before its use on Mars. A testing program has been conducted with flight-like instruments to acquire science data relevant to the interpretation of the Mars experiment. Factors involved in the delineation of a positive result are presented and the significance of the possible results discussed.     

A new chromogenic substrate for subtilisin

A new chromogenic substrate, benzyloxycarbonyl-glycyl-glycyl-l-leucine p-nitroanilide, was synthesiszed allowing convenient spectrophotometric assay of subtilisin activity. This substrate has been applied to the determination of subtilisin in solution as well as for the identification of subtilisin after gel electrophoresis or isoelectrophocusing. Catalytic parameters for the new substrate were determined.