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Spermatozoa have a defined function, that is, the fertilization of an egg. To achieve this goal, spermatozoa have to move actively toward the egg and inject the male pronucleus into the egg. Therefore, sperm motility is one of the crucial determinants for male fertility. Surprisingly, however, structure and energy metabolism can differ substantially between spermatozoa from different species. Here
Activation of the cyclin-dependent kinases to promote cell cycle progression requires their association with cyclins as well as phosphorylation of a threonine (residue 161 in human p34(cdc2)). This phosphorylation is carried out by CAK, the Cdk-activating kinase. We have purified and cloned CAK from S. cerevisiae. Unlike CAKs from other organisms, Cak1p is active as a monomer, has full activity wh
Creatine kinase (CK) isoenzymes, with emphasis on the mitochondrial CK isoenzymes, were characterized and localized in chicken cerebellum. Chicken cerebellar extracts analyzed by two-dimensional gels, using anti-peptide antibodies specific for sarcomeric muscle-type mitochondrial CK (Mib-CK) and revealed the presence of a Mib-CK variant in avian cerebellum. This CK isoform was localized by immunof
The creatine kinase (CK) isoenzyme system is essential for motility in rooster and sea urchin sperm. In the present study, biochemical characterization as well as immunofluorescence and confocal laser microscopy with highly specific antibodies against various chicken CK isoenzymes revealed that cytosolic brain-type CK isoenzyme (B-CK) is the only CK isoenzyme in rooster seminal plasma, while three
Mitochondrial creatine kinase (Mi-CK) consists of octameric and dimeric molecules that are interconvertible. In the present study, the kinetic properties of purified chicken heart Mi-CK (Mi(b)-CK) dimers and octamers were investigated separately under highly controlled conditions. Gel-permeation chromatography was performed before and after kinetic measurements in order to clearly define the propo
An interaction of mitochondrial creatine kinase with purified outer mitochondrial porin (voltage-dependent anion channel) was shown by co- sedimentation assays as well as by gel permeation chromatography. Porin formed high M(r) complexes with wild-type mitochondrial creatine kinase as well as with an N-terminal deletion mutant, lacking the first five N-terminal amino acids. The complexes were iden
Mitochondrial creatine kinase (Mi-CK) isoenzymes, in contrast to cytosolic CKs, form octameric molecules composed of four stable dimers. Octamers and dimers are interconvertible. Removal of the N-terminal pentapeptide of chicken cardiac Mi-CK (Mib-CK) by limited proteolysis drastically destabilized the octamer. The role of the charged amino acids within the N-terminal heptapeptide was studied in d
Sarcomeric mitochondrial creatine kinase (Mi(b)-CK) of chicken was expressed in Escherichia coli as a soluble enzyme by using an inducible phage-T7 promoter. Up to one third of the protein in E. coli extracts consisted of soluble recombinant Mi(b)-CK in an enzymically active form. Approx. 20 mg of nearly-homogenous Mi(b)-CK was isolated in a two-step isolation procedure starting with 1 litre of is
Since 2010 when the North American ELKHORN and Baltoscandic PAROVEJA isotope excursions were first described and named, their mutual age relations have remained uncertain, if not controversial. This was at least partly due to the incompleteness of the ELKHORN excursion in its reference section in western Ohio. The unexpected discovery of an apparently complete ELKHORN excursion in a drill core fro
The effect that extreme natural events have on biological diversity is relatively poorly known. We used a before–after control-impact (BACI) design to analyze changes in bird abundances and communities following Hurricane Gudrun, which struck southern Sweden in January 2005, felling 75 million m3 of forest and causing damage to 5% of forested areas (half a million hectares) in a few hours. We used
Urban resilience to natural and human-induced shocks and stresses has become an important issue in the contemporary world. Several reviews exist on urban resilience, but limited attempts have been made to critically review studies that shed light on determinants of urban resilience in sub-Saharan Africa (SSA). This study synthesizes both peer-reviewed and grey literature on the determinants of urb
Monitoring soil moisture at the Earth'surface is of great importance for drought early warnings. Spaceborne remote sensing is a keystone in monitoring at continental scale, as satellites can make observations of locations which are scarcely monitored by ground-based techniques. In recent years, several soil moisture products for continental scale monitoring became available from the main space age
