Possible identity of a membrane-bound with a soluble cyclic AMP-independent erythorocyte protein kinase that phosphorylates spectrin

A soluble casein kinase isolated and purified to homogeneity from the human erythrocyte cytosol by phosphocellulose and Sephadex G-200 chromatographies is indistinguishable from the membrane-bound casein (spectrin_kinase according and site-specificity criteria. The soluble enzyme shows an M_r of about 30 000 by gel filtration and comigrates with the purified membrane spectrin kinase as a single polypeptide of 32 000 Da on sodium dodecyl sulfate polyacrylamide gels. The soluble kinase phosphorylates spectrin in situ in spectrin kinase-depleted ghosts and catalyzes the in vitro phosphorylation of partially dephosphorylated spectrin with saturation kinetics identical to those displayed by the membrane spectrin kinase. When component 2 of spectrin that has been phosphorylated with [γ-³²P]ATP by either the soluble or the membrane kinases was subjected to limited proteolysis, the same 21500 Da papain-generated phosphopeptide was found to have been produced by the two enzymes. The same 21 500 Da phosphopeptide was identified after papain digestion of spectrin isolated from intact cells that had been incubated with ³²P_i. However, this particular peptide was not labeled in spectrin that had been phosphorylated in vitro by the catalytic subunit of cyclic AMP-dependent protein kinase. Identical phosphopeptide patterns were obtained by gel filtration and two-dimensional peptide maps of trypsin-cleaved component 2 of spectrin that had been labeled in situ, in intact ghosts or in spectrin kinase-depleted ghosts supplemented with the soluble kinase. These findings indicate a possible identity of the soluble with the membrane-bound casein (spectrin) kinase.     

Syngeneic leukemia models using lentiviral transgenics

Animal models are necessary to study cancer and develop treatments. After decades of intensive research, effective treatments are available for only a few types of leukemia, while others are currently incurable. Our goal was to generate novel leukemia models in immunocompetent mice. We had achieved abilities for overexpression of multiple driving oncogenes simultaneously in normal primary cells, which can be transplanted and followed in vivo. Our experiments demonstrated the induction of primary malignant growth. Leukemia lines that model various types of leukemia, such as acute myeloid leukemia (AML) or chronic lymphocytic leukemia (CLL), were passaged robustly in congenic wild-type immunocompetent mice. These novel leukemia lines, which may complement previous models, offer the flexibility to generate tailored models of defined oncogenes of interest. The characterization of our leukemia models in immunocompetent animals can uncover the mechanisms of malignancy progression and offer a unique opportunity to stringently test anti-cancer chemotherapies.Subject terms: Cancer models, Haematopoietic stem cells, Leukaemia     

Novel cyclic azo-bridged analogs of gonadotropin-releasing hormone.

Five linear analogs of GnRH containing a p-aminophenylalanine (Pap) residue in their sequence and their six corresponding azo-bridged cyclic derivatives were synthesized. The precyclic peptides were prepared on solid-support, while azo-cyclization was performed in solution by diazotization of the p-aminophenylalanine residue followed by intramolecular coupling of the formed diazo salt with either tyrosine or histidine side chains present in the sequence. All peptides were examined for their binding ability to the GnRH receptor expressed on rat pituitary membranes and for their LH-release activity from dispersed rat pituitary cells. Linear analogs 1 i.e [Pap(5)] GnRH and 3, i.e. [Tyr(3), Pap(5)] GnRH, were found to bind to the GnRH receptors only slightly less avidly than native GnRH. Their cyclization, however, led to a marked reduction in the binding capacity, i.e. from IC(50) of 10(-9) M to the 10(-7) M range, and in biopotency, i.e. LH-release. All other linear and cyclic peptides were found to bind selectively to the GnRH receptor only in the low microM range. Only peptide 1 was found comparable to native GnRH in respect to LH-release activity and thus may potentially be a good agonist of the parent peptide. Peptides 1-4, the most potent GnRH receptor binders, were examined for their conformational properties using CD. Cyclic-azo peptides 2 and 4 were further evaluated by NMR spectroscopy in solution combined with molecular modeling. The structural information obtained explains in part the GnRH-like biological activity observed.     

Water response of the hygrochastic skeletons of the true rose of Jericho (Anastatica hierochuntica L.)

Summary The hygrochastic apparatus in Anastatica hierochuntica was investigated from the standpoint of morphology of the skeleton and fruit and its contribution to the regulation of seed dispersal in accordance with the water conditions.Water absorption by the dry skeletons upon shoot immersion under laboratory conditions is a rapid process requiring only a few minutes. It is followed by a slow opening of the curled branches of the skeleton. Maximal opening is attained by the saturated skeletons in approximately 2h. Absorption of water and subsequent opening occur also when only the main root of the skeleton is immersed in water. The process was duplicated also by intact skeletons irrigated in situ. Skeletons closure in response to evaporation is initially slow, noticable curling of the branches obtained only after 60% of the water is lost from the saturated skeletons. Opening of the skeleton exposes most of the fruits to the force of falling raindrops. The fact that no spontaneous opening of fruits occurred under most laboratory procedures of skeleton immersion suggests that in nature two successive processes occur: the skeletons must first uncurl-hygrochasticly so that raindrops can impinge forcefully on the appendages of the fruit valves and thus cause seed release by ombrohydrochory. Under adequate rainfall, the first fruits to open are those at the outer infructescences; heavier rainfall will release seeds from the upper fruits of the inner infructescences, and later, from fruits at their bases. The force that binds the valves of the fruits to the septa is variable, its strength correlated with different structure of the fruist at different positions on the skeleton. This ensures a rate of seed release commensurate with the rainfall, and secures at least a minimum of water for the first seeds. The heterogeneity of skeleton populations insofar as age of the plants is concerned, further ensures that seed dispersal in a given area will be proportional to the amount of rainfall.     

Properties of laccase in Schinus molle

The properties of laccase isolated from Schinus molle, including its MW, amino acid and carbohydrate composition, are described. The enzyme is distinct from Rhus laccase both in K_m and in carbohydrate composition.