Combined deficiency in vitamin K-dependent (VKD) coagulation factors is an autosomal recessive bleeding disorder associated with defects in either the VKD carboxylase which converts Glus to Glas in ...VKD proteins to render them active or the vitamin K epoxide reductase (VKORC1) which supplies the reduced vitamin K cofactor required for carboxylation. Such defects are rare, and we now report the fourth case of deficiency caused by mutations in the carboxylase gene. The mutations were identified in a two year old Tunisian girl who exhibited impaired function in several VKD procoagulant and anticoagulant factors that was not restored by vitamin K administration. Sequence analysis of the propositus did not identify any mutations in the VKORC1 gene but, remarkably, revealed three heterozygous mutations in the carboxylase gene, D31N, W157R and T591K within exons 2, 4 and 13, respectively. None of these mutations have previously been reported. Family analysis showed that D31N and T591K were coallelic and transmitted by the mother while W157R was transmitted by the father. The mutations were not found in the genomes of 200 normal subjects, ruling out frequent polymorphisms. Mutational analysis indicated wild type activity for the D31N carboxylase. In contrast, the W157R and T591K enzymes had activities that were, respectively, 7% and 0% that of wild type carboxylase, and their compound heterozygosity can therefore account for defective carboxylation. Residues 157 and 591 are both highly evolutionarily conserved, and residue 157 lies within a region previously suggested to be important for carboxylase binding to VKD Glus or propeptide. However, the hydrophobic nature of this region and inability of vitamin K administration to restore VKD protein function alternatively suggests that residue 157 may be important for vitamin K binding.
Xylem sap composition of spruce is influenced by several factors, such as the sampled organ, the sampling period, the availability of soil nutrients, and the soil water potential. Based on literature ...data and ongoing investigations carried out with adult trees, we present an overview on the main factors influencing xylem sap concentrations of Norway spruce. Direct measurements of nutrient fluxes in the xylem sap are then used to suggest a general scheme of mineral element cycling within adult trees. In Norway spruce (Picea abies Karst.), nutrient concentration in the xylem sap was higher in twigs and fine roots compared to the bottom of the trunk, the highest concentrations beeing observed in spring during the shoot elongation. Xylem sap concentrations were higher in spruce growing at nutrient rich sites than at poor sites. The combination of twig and trunk xylem sap analysis, together with xylem flow measurements in the trunk during the course of a vegetation period allowed the quantification of mineral fluxes via xylem sap flow in the trunk and twigs. These results were compared to gross mineral uptake measurements at the same site. Ca flux in the trunk xylem sap was lower than the gross uptake of Ca. Mg flux in trunk sap was approximately equivalent to Mg gross uptake whereas P and K fluxes in trunk sap were much higher than the gross uptake. Fluxes of Ca, Mg, K and P in the twig sap were much higher than that in trunk sap. Data suggest that internal cycling is responsible for a large part of the nutrient fluxes in the xylem sap of the crown. Xylem sap composition thus appears to be a tool which can complement other sources of information on mineral uptake and cycling in adult spruce.
The vitamin K-dependent (VKD) carboxylase converts clusters of Glu residues to γ-carboxylated Glu residues (Glas) in VKD proteins,
which is required for their activity. VKD precursors are targeted ...to the carboxylase by their carboxylase recognition site,
which in most cases is a propeptide. We have identified a second tethering site for carboxylase and VKD proteins that is required
for carboxylase activity, called the vitamin K-dependent protein site of interaction (VKS). Several VKD proteins specifically
bound an immobilized peptide comprising amino acids 343â355 of the human carboxylase (CVYKRSRGKSGQK) but not a scrambled peptide
containing the same residues in a different order. Association with the 343â355 peptide was independent of propeptide binding,
because the VKD proteins lacked the propeptide and because the 343â355 peptide did not disrupt association of a propeptide
factor IX-carboxylase complex. Analysis with peptides that overlapped amino acids 343â355 indicated that the 343â345 CVY residues
were necessary but not sufficient for prothrombin binding. Ionic interactions were also suggested because peptide-VKD protein
binding could be disrupted by changes in ionic strength or pH. Mutagenesis of Cys 343 to Ser and Tyr 345 to Phe resulted in 7â11-fold decreases in vitamin K epoxidation and peptide (EEL) substrate and carboxylase carboxylation,
and kinetic analysis showed 5â6-fold increases in K
m values for the Glu substrate. These results suggest that Cys 343 and Tyr 345 are near the catalytic center and affect the active site conformation required for correct positioning of the Glu substrate.
The 343â355 VKS peptide had a higher affinity for carboxylated prothrombin ( K
d = 5 μ m ) than uncarboxylated prothrombin ( K
d = 60 μ m ), and the basic VKS region may also facilitate exiting of the Gla product from the catalytic center by ionic attraction.
Tethering of VKD proteins to the carboxylase via the propeptide-binding site and the VKS region has important implications
for the mechanism of VKD protein carboxylation, and a model is proposed for how the carboxylase VKS region may be required
for efficient and processive VKD protein carboxylation.
Key Findings: * As a whole, Turnaround Strategy efforts are producing improvements in math performance in targeted schools. We did not find evidence of positive impacts of schoolwide targeted support ...on other student outcomes. * There is little evidence that support from math and reading specialists―one component of the Turnaround Strategy in targeted schools―had an impact on academic outcomes. * We found no evidence that the CIS case management component of the Turnaround Strategy improved student suspensions, attendance, or academic achievement. * Turnaround partnership schools are producing improvements in math performance. However, other effects were mixed, varying by outcome and by partner organization. This is the second report on Year 2 of the Strategy, following an interim report (Hallgren et al. 2018) that presented detailed implementation findings in targeted and partnership schools after the second year of the Strategy (2017–2018). This report analyzes the impact of the Strategy in targeted schools after two years and the effectiveness of two specific intervention components offered in those schools in 2017–2018: (1) math and reading specialists, and (2) Communities in Schools (CIS) case management. It also analyzes the impact of the Kindezi and PBS school partnerships. For each of the analyses, we also provide implementation information as context for the impact findings.
The South Pole Acoustic Test Setup (SPATS) was built to evaluate the acoustic characteristics of the South Pole ice in the 10 kHz to 100 kHz frequency range, for the purpose of assessing the ...feasibility of an acoustic neutrino detection array at the South Pole. The SPATS hardware consists of four vertical strings deployed in the upper 500 m of the South Pole ice cap. The strings form a trapezoidal array with a maximum baseline of 543 m. Each string has 7 stages equipped with one transmitter and one sensor module. Sound is detected or generated by piezoelectric ceramic elements inside the modules. Analogue signals are sent to the surface on electric cables where they are digitized by a PC-based data acquisition system. The data from all strings are collected on a central computer in the IceCube Laboratory from where they are send to a central data storage facility via a satellite link or stored locally on tape. A technical overview of SPATS and its performance is presented.
PDF