Nucleotide sequence of the second psbG gene in Synechocystis 6803. Possible implications for psbG function as a NAD(P)H dehydrogenase subunit gene

Nucleotide sequencing of the second Synechocystis 6803 psbG gene, psbG2 shows the predicted polypeptide to be 219 amino acids long. It is less similar to chloroplast psbG genes than is the Synechocystis psbG1 copy. Alignment with seven other psbG protein sequences, including that from the Paramecium mitochondrial genome reveals a central highly conserved region common to each. This is discussed as evidence supporting the proposal that the psbG polypeptide is a NAD(P)H dehydrogenase (complex I) subunit in cyanobacteria, chloroplasts and mitochondria.     

Spiggin levels are reduced in male sticklebacks infected with Schistocephalus solidus

Using an enzyme-linked immunosorbent assay (ELISA) based technique, Schistocephalus solidus infection was shown to considerably reduce levels of spiggin in the kidney of male three-spined sticklebacks Gasterosteus aculeatus from an oligotrophic upland lake. These results suggested a graduated effect of the infection on the reproductive physiology of male three-spined sticklebacks.     

Methods of tracing hydrogen in polyketide biosynthesis: High field NMR spectroscopy of citrinin produced in a D2O based medium

Penicillium citrinum cultures have been germinated on an H₂O-based medium, resuspended on a D₂O-based medium and treated with [l,2-¹³C₂] acetate. The resulting citrinin (1) has been analysed by²H and¹³C nuclear magnetic resonance spectroscopy and information about the metabolism of hydrogen in citrinin biosynthesis has been deduced.     

Radiation inactivation analysis of assimilatory NADH:nitrate reductase. Apparent functional sizes of partial activities associated with intact and proteolytically modified enzyme

Recently we demonstrated that target sizes for the partial activities of nitrate reductase were considerably smaller than the 100-kDa subunit which corresponded to the target size of the full (physiologic) activity NADH:nitrate reductase. These results suggested that the partial activities resided on functionally independent domains and that radiation inactivation may be due to localized rather than extensive damage to protein structure. The present study extends these observations and addresses several associated questions. Monophasic plots were observed over a wide range of radiation doses, suggesting a single activity component in each case. No apparent differences were observed over a 10-fold range of concentration for each substrate, suggesting that the observed slopes were not due to marked changes in Km values. Apparent target sizes estimated for partial activities associated with native enzyme and with limited proteolysis products of native enzyme suggested that the functional size obtained by radiation inactivation analysis is independent of the size of the polypeptide chain. The presence of free radical scavengers during irradiation reduced the apparent target size of both the physiologic and partial activities by an amount ranging from 24 to 43%, suggesting that a free radical mechanism is at least partially responsible for the inactivation. Immunoblot analysis of nitrate reductase irradiated in the presence of free radical scavengers revealed formation of distinct bands at 90, 75, and 40 kDa with increasing doses of irradiation rather than complete destruction of the polypeptide chain.     

Characterization of the chicken oocyte receptor for low and very low density lipoproteins

The chicken oocyte receptor for low and very low density lipoproteins has been identified and characterized. Receptor activity present in octyl-beta-D-glucoside extracts of oocyte membranes was measured by a solid phase filtration assay, and the receptor was visualized by ligand blotting. The protein had an apparent Mr of 95,000 in sodium dodecyl sulfate-polyacrylamide gels under nonreducing conditions and exhibited high affinity for apolipoprotein B-containing lipoproteins, but not for high density lipoproteins or lipoproteins in which lysine residues had been reductively methylated. Binding of lipoproteins was sensitive to EDTA, suramin, and treatment with Pronase. In these aspects, the avian oocyte system was analogous to the mammalian low density lipoprotein receptor in somatic cells. Furthermore, a structural relationship between the mammalian and avian receptors was revealed by immunoblotting: polyclonal antibodies directed against the purified bovine low density lipoprotein receptor reacted selectively with the 95-kDa chicken receptor present in crude oocyte membrane extracts.