Characterization of the high affinity heparin binding site of the Alzheimer's disease βA4 amyloid precursor protein (APP) and its enhancement by zinc(II)

The Alzheimer's disease βA4 amyloid precursor protein (APP) has been shown to be involved in a diverse set of biological protein precursor-like proteins (APLP1 and APLP2) belong to a superfamily of proteins that are probably functionally related. In order to characterize the cell adhesion properties of APP the brain specific isoform APP₆₉₅ was purified and used to assess the binding to herparin, a structural and functional analogue of the glycosaminoglycan heparan sulfate. We show that APP binds in a time dependent and saturable manner to heparin. The salt concentration of 620 mM at which APP elutes from heparin Sepharose is greater than physiological. Tha apparent equilibrium constant for dissociation was determined to be 300 pM for APP binding to heparin Sepharose. A high affinity heparin binding site was identified within a region conversed in rodent and human APP, APLP1 and APLP2. This binding site was located between residues 316-337 of APP₆₉₅ which is within the carbohydrate domain of APP. We also demonstrate an interaction between this heparin binding site and the zinc(II) binding site which is conserved in all members of the APP superfamily. We show by using an automated surface plasmon resonance biosensor (BIAcore, Pharmacia) that the affinity for heparin is increased two- to four-fold in the presence of micromolar zinc(II). The identification of zinc-enhanced binding of APP to heparin sulfate side chains of proteoglycans offers a molecular link between zinc(II), as a putative environmental toxin for Alzheimer's disease, and aggregation of amyloid βA4 protein.     

Avian feather development: relationships between morphogenesis and keratinization

Morphogenesis and expression of the alpha and beta keratin polypeptides are controlled by epidermal-dermal interactions during development of avian skin derivatives. We have examined the relationship between morphogenesis of the embryonic feather and expression of the feather alpha and beta keratins by routine histology, indirect-immunofluorescence, and SDS-PAGE. Initially beta keratins are expressed only in the feather sheath. Following barb ridge morphogenesis beta keratins can be detected in the barb ridge, coincident with the differentiation of barb ridge cells into eight distinct morphological types. Beta keratinization occurs in gradients; from feather apex to base, and from periphery of the barb ridge to the interior. The onset of beta keratinization in the barb ridges is paralleled by an increase in the major feather beta keratin polypeptides, as detected by SDS-PAGE. The alpha keratins are present in both the periderm and feather sheath at early stages of feather development, but become greatly reduced after hatching, when the down feather emerges from the sheath.     

Nucleotide sequence of the O gene and of the origin of replication in bacteriophage lambda DNA.

The nucleotide sequence of the O gene in bacteriophage lambda DNA is presented. According to two possible initiator codons, the primary structure of the O protein deduced from the DNA sequence consists of 278 or 299 amino acid residues. Structure and function of the O protein--one of the two phage initiator proteins for lambda DNA replication--are discussed in the light of a secondary structure model for the O protein. The central part of the O gene contains a cluster of symmetrical sequences extending over 160 base pairs. The point mutation of the cis-dominant replication mutant ti12 is located in this region.     

Macromolecular Synthesis and Degradation in Arthrobacter During Periods of Nutrient Deprivation

Cells of Arthrobacter atrocyaneus and A. crystallopoietes, harvested during their exponential phase, were starved in 0.03 M phosphate buffer (pH 7.0) for 28 days. During this time, the cells maintained 90 to 100% viability. Experimental results were similar for both organisms. Total cellular deoxyribonucleic acid was maintained. Measurable degradation rates for deoxyribonucleic acid as determined by radioisotope techniques were not observed, and only during the initial hours of starvation could a synthetic rate be determined. Total ribonucleic acid levels remained stable for the first 24 h of starvation, after which slow, continuous loss of orcinol-reactive material occurred. Synthetic and degradative rates of ribonucleic acid, as determined by radioisotope techniques, dropped quickly at the onset of starvation. Constant basal rates were attained after 24 h. In A. atrocyaneus, total cell protein was degraded continuously from the onset of starvation. In A. crystallopoietes, total cell protein remained stable for the first 24 h, after which slow continuous loss occurred. After 28 days, the total protein per cell was similar for both organisms. In the first week, amino acid pools stabilized at about 50% of the values characteristic of growth. Rates of degradation of protein decreased rapidly for the first 24 h for both organisms, but leveled to a constant basal rate thereafter. Rates of new protein synthesis dropped during the first 24 h and by 48 h achieved a constant basal rate.     

Molecular genetics of mutants of Rhizobium leguminosarum which fail to fix nitrogen

Summary Mutants of Rhizobium leguminosarum which failed to fix nitrogen within nodules on peas were isolated following the insertion of the transposon Tn5 into pRL1JI, a Rhizobium plasmid known to carry the genes for nitrogenase. The sites of the Tn5 insertions were identified by restriction endonuclease mapping of cloned fragments of DNA from the mutant strains. One group of mutants was located within 4 kilobases of the structural genes for nitrogenase and another was located about 30 kilobases from this region. Two mutants from the first group, one of which appeared to be affected in a nitrogenase gene, induced nodules that contained bacterioids, but the number of plant cells containing bacteroids was less than in a normal nodule. Another group of mutants, which was located about 30 kilobases from the nitrogenase genes failed to form bacterioids. Electron microscopy of the nodules induced by these mutants indicated that there was a defect in their release from infection threads.     

Assignment of proximal histidyl imidazole exchangeable proton NMR resonances to individual subunits in hemoglobins A,Boston, Iwate and Milwaukee

The proton nmr spectra of the synthetic valency hybrids, α₂(β⁺CN)₂, (α⁺CN)₂β₂ of hemoglobin A and the natural valency hybrids of the mutant hemoglobins Boston, Iwate and Milwaukee have led to the unambiguous assignment of the two proximal histidyl imidazole exchangeable proton signals at 64 and 76 ppm to individual α and β subunits, respectively. New single non-exchangeable proton resonances detected in the extreme downfield region of the spectra of Hbs Boston and Iwate are tentatively assigned to the coordinated tyrosine of the mutated α chains.     

Stimulation of growth and phospholipase A2 by the peptides mastoparan and melittin and by the auxin 2,4-dichlorophenoxyacetic acid

The peptide mastoparan from wasp venom and the peptide melittin from bee venom stimulated growth in etiolated zucchini (Cucurbita pepo L.) hypocotyls. Both peptides were only effective in hypocotyls with abraded cuticles. At concentrations of 2 g ml^–1 peptide growth was stimulated 72% by mastoparan and 50% by melittin after 2 h as compared to the controls. Mastoparan (5 g ml^–1), melittin (10 g l^–1) and 2,4-dichlorophenoxyacetic acid (5×10^–4 M) stimulated accumulation of ¹⁴C-choline-labeled lysophosphatidylcholine in less than 10 min in cultured soybean cells (Glycine max L.), all to about the same extent. The effects of these peptides are among the first to be reported on plant cells and may be related to important events coupled to growth stimulation.Abbreviations 2,4-D 2,4-dichlorophenoxyacetic acid     

Apolipoprotein A-IV polymorphism in man

Summary In man, apolipoprotein A-IV is characterized by a genetically determined polymorphism controlled by two codominant alleles. Two isoforms of this apolipoprotein, designated A-IV-1 and A-IV-2, can be identified by isoelectric focusing. Among 1000 healthy factory workers participating in an epidemiological study, A-IV-1 (genotype 1-1) was observed in 85%; A-IV-2 (genotype 2-2), in 0.5%; and A-IV-1 in combination with A-IV-2 (genotype 1–2), in 14%. In four nonrelated subjects, an apolipoprotein A-IV variant (A-IV-Münster), characterized by a slightly more basic isoelectric focusing behavior than A-IV-2, was detected in combination either with A-IV-1 or A-IV-2. Mendelian inheritance of this variant could be demonstrated.