Binding of Calcium and Magnesium to Cardiac Troponin C

AbstractCardiac troponin C (cTnC) is the Ca2+-sensing component of the thin filament. It contains structural sites (III/IV) which bind both Ca2+and Mg2+, and a regulatory site (II) that has been thought to bind only Ca2+. The latter binding initiates a series of conformational changes that culminate in force production.We have quantified the interaction between site II and Ca2+/Mg2+through Isothermal Titration Calorimetry and Thermodynamic Integration simulations. Direct and competitive binding titrations using wild type and a double mutant that significantly reduces binding to site II demonstrated that physiologically relevant concentrations of both Ca2+/Mg2+interact with the same locus. Cytosolic free Mg2+(~1 mM) could occupy a significant population of available site II, as this concentration of Mg2+decreased the affinity for Ca2+1.4-fold.Interaction of Mg2+with site II of cTnC likely has important functional consequences for the heart at baseline and in diseased states which decrease or increase availability of Mg2+such as secondary hyperparathyroidism or ischemia, respectively.</jats:p

An investigation of assumptions made in estimating genetic parameters and predicting genetic gain in a Eucalyptus nitens breeding programme in South Africa

It is important to have an understanding of the population genetics and validity of the pertinent underlying assumptions of a species in order to design an effective breeding strategy. In a South African breeding population of Eucalyptus nitens, various scenarios investigating a range of assumptions were developed and used to predict genetic gain in the F2. These were compared with realised gains achieved in a series of genetic gain trials. In the two scenarios using firstly, actual flowering for family (provenance) and, secondly, estimated flowering after 30 % roguing of poor families, a coefficient of relationship of 0.33 resulted in predictions closest to realised gain, on average. The statistical information suggested that outcrossing in the seed orchards was[80 %. Indications were that the effects were additive, and that very little or no heterosis had occurred, due to the still significant provenance effects and the lack of provenance rank changes in the F2. The custom of assuming a degree of inbreeding (and using a coefficient of relationship of 0.33) and of including provenance effects in the models, on average resulted in genetic gain predictions which were very similar to the realised genetic gains in this population of E. nitens.Masonite Ltd., Mondi Ltd, NCT Forestry Co-Operative Ltd., PG Bison, TWK Ltd. and York Timbers Ltd.http://link.springer.com/journal/110562016-01-31hb201