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J McCourt

Publications and source records attributed to J McCourt.

5 recordsLinked to original sources
PubMed1999

Lysine: N6-hydroxylase: stability and interaction with ligands.

Recombinant lysine:N6-hydroxylase, rIucD, which is isolated as an apoenzyme, requires FAD and NADPH for its catalytic function. rIucD preparations have been found to undergo time-dependent loss in monooxygenase function due to aggregation from the initial tetrameric state to a polytetrameric form(s), a process which is reversible by treatment with thiols. Ligand-induced conformational changes in rIucD were assessed by monitoring its CD spectra, DSC profile, and susceptibility to both endo- as well as exopeptidases. The first two methods indicated the absence of any significant conformational change in rIucD, while the last approach revealed that FAD, and its analog ADP, can protect the protein from the deleterious action of proteases. NADPH was partially effective and L-lysine was ineffective in this regard. Deletion of the C-terminal segment, either by treatment with carboxypeptidase Y or by mutagenesis of iucD, results in the loss of rIucD's monooxygenase activity. These findings demonstrate the crucial role of the C-terminal segment in maintaining rIucD in its native conformation.

Adenosine Diphosphate↗
PubMed1996

Trace metals in the marine bivalve Macoma balthica in the Westerschelde estuary, The Netherlands. Part 3: variability of the role of cytosol in metal uptake by the clams.

Tellinid clams Macoma balthica were sampled every 2 months for 2.5 years at two locations from the Westerschelde estuary (The Netherlands) and submitted to in vitro short-term exposure to Cd, Cu and Zn. Total and heat-stable cytosolic metal concentrations have been measured before and after exposure to study the effects of the sampling season on metal uptake by the bivalve. We observed much higher uptakes of Cd and, to a lesser extent, Cu in winter than in summer, while Zn appears to be constantly regulated. These phenomena are amplified in the cytosol, especially for Cd, a non-essential element, for which the concentrations after exposure can reach 3.5-4 microg x g-1 (dry wt.) in winter, but only a maximum of 0.5 microg x g-1 in summer, all natural values being between 0.01 and 0.1 microg x g-1 on average. The contents (microg) of the various elements, either at the total or at the cytosolic level, are not constant, hence showing that the seasonal body weight fluctuation of the clams (dilution or concentration effect) is not the only parameter responsible for the metal uptake variability. Furthermore, we have shown that the proportion of cytosolic metal is not constant, but increases with the absolute cytosolic concentration up to 35-40%. Therefore, the cytosolic phase of the cells plays a growing role in Cd, Cu and Zn storage as long as their total concentration increases.

Animals↗
PubMed1995

Developmental role of perceived parental control in the eating psychopathology of Asian and Caucasian schoolgirls.

It has been suggested that the relatively high levels of eating psychopathology among Asian schoolgirls living in the United Kingdom are due to "culture clash," but this construct needs further definition. A recent study has shown that perceived control by family members is important in determining the relatively unhealthy eating attitudes of Asian adolescents. However, that study focused on older adolescents (aged 14-15 years). The present study examines the development of that effect in a sample of Asian and Caucasian adolescent girls with a broader range of ages (aged 12-16 years). Again, the unhealthy eating attitudes of Asian girls were partly explained by their high levels of perceived maternal control. However, this effect was particularly strong among the older girls, suggesting a developmental trend through adolescence. There might be clinical benefits of addressing perceived or actual maternal control in these girls.

Adolescent↗