Characterization of Microtubule-Associated Protein 2 from Mouse Brain and Its Localization in the Cerebellar Cortex

Microtubule-associated protein (MAP) 2 was purified from the microtubule fraction of mouse brain by heat treatment and BioGel A-5m gel filtration. The purified preparation showed a single protein band on sodium dodecyl sulfate-polyacrylamide gel electrophoresis using both a gradient gel (3.75-12.5%) and a low-percentage gel (5%), a finding indicating that MAP2B was absent under the conditions used. Amino acid analysis revealed that mouse MAP2 was an acidic protein with an isoelectric point (pI 4.5) and amino acid composition similar to those of porcine brain MAP2. Immunoblot analysis indicated that the antigens that reacted with MAP2 antiserum were present in large quantities in mouse brain. However, we also found a weak reaction in various tissues other than brain, and the major antigens involved were recognized to be common molecular species with the same molecular mass, 162 and 170 kilodaltons. Using antiserum against mouse brain MAP2, the developmental localization patterns of MAP2 in the mouse cerebellar cortex were studied by immunohistochemistry. MAP2 was mainly localized in the neuronal cells throughout development, with the expression in Purkinje cell dendrites being especially remarkable in the growth of arborization from postnatal day 3 to day 20. At the mature stage, the reaction was strong in the dendritic tree but very weak in the proximal dendrites and cell bodies.     

A flexible method to align large numbers of biological sequences

Summary A method for the alignment of two or more biological sequences is described. The method is a direct extension of the method of Taylor (1987) incorporating a consensus sequence approach and allows considerable freedom in the control of the clustering of the sequences. At one extreme this is equivalent to the earlier method (Taylor 1987), whereas at the other, the clustering approaches the binary method of Feng and Doolittle (1987). Such freedom allows the program to be adapted to particular problems, which has the important advantage of resulting in considerable savings in computer time, allowing very large problems to be tackled. Besides a detailed analysis of the alignment of the cytochrome c superfamily, the clustering and alignment of the PIR sequence data bank (3500 sequences approx.) is described.     

Probing FhuA''-''PhoA fusion proteins for the study of FhuA export into the cell envelope of Escherichia coli K12

Summary The FhuA protein (formerly TonA) is located in the outer membrane of Escherichia coli K12. Fusions between fhuA and phoA genes were constructed. They determined proteins containing a truncated but still active alkaline phosphatase of constant size and a variable FhuA portion which ranged from 11%–90% of the mature FhuA protein. The fusion sites were nearly randomly distributed along the FhuA protein. The FhuA segments directed the secretion of the truncated alkaline phosphatase across the cytoplasmic membrane. The fusion proteins were proteolytically degraded up to the size of alkaline phosphatase and no longer reacted with anti-FhuA antibodies. The fusion proteins were more stable in lon and pep mutants lacking cytoplasmic protease and peptidases, respectively. The larger fusion proteins above a molecular weight of 64000 dalton were predominantly found in the outer membrane fraction. They were degraded by trypsin when cells were converted to spheroplasts so that trypsin gained access to the periplasm. In contrast, FhuA protein in the outer membrane was largely resistant to trypsin. It is concluded that the larger FhuA-PhoA fusion proteins were associated with, but not properly integrated into, the outer membrane.     

Identification, cloning, nucleotide sequence and chromosomal map location of hns, the structural gene for Escherichia coli DNA-binding protein H-NS

Summary Beginning with a synthetic oligonucleotide probe derived from its amino acid sequence, we have identified, cloned and sequenced the hns gene encoding H-NS, an abundant Escherichia coli 15 kDa DNA-binding protein with a possible histone-like function. The amino acid sequence of the protein deduced from the nucleotide sequence is in full agreement with that determined for H-NS. By comparison of the restriction map of the cloned gene and of its neighboring regions with the physical map of E. coli K12 as well as by hybridization of the hns gene with restriction fragments derived from the total chromosome, we have located the hns gene oriented counterclockwise at 6.1 min on the E. coli chromosome, just before an IS30 insertion element.     

Characterization of a delayed rectifier K+ channel in NG108-15 neuroblastomaX glioma cells: Gating kinetics and the effects of enrichment of membrane phospholipids with arachidonic acid

Summary The calcium sensitivity of exocytosis from electroper-meabilized chromaffin cells is increased by activators of protein kinase C, such as TPA and certain phorbol esters, diacylglycerols, and mezerein. A range of putative inhibitors of protein kinase C block both the phorbol ester-sensitive component of secretion and also the underlying insensitive component. These inhibitors are also shown to inhibit medulla protein kinase C activity in vitro. The extent of secretion is reduced when electropermeabilized cells are exposed to Ca²⁺ levels much in excess of 50 m. The onset of inhibition is faster than the relatively slow rate of Ca-dependent exocytosis and is insensitive to inhibitors of proteolysis. Adrenal medulla protein kinase C activity is also irreversibly inhibited by high Ca²⁺ concentrations. Both the secretory response and the protein kinase C activity in vitro have similar nucleotide and cation specificities. Although these data do not definitely establish an involvement of protein kinase C in exocytosis, none argue against it.Deceased     

Preparation and characterisation of monoclonal and polyclonal antibodies to maize membrane auxin-binding protein

Binding proteins, thought to be auxin receptors, can be solubilised from maize (Zea mays L.) membranes after acetone treatment. From these crude extracts, receptor preparations of over 50% purity can be obtained by a reliable, straight-forward procedure involving three chromatographic steps — anion exchange, gel filtration and high-resolution anion exchange. Such preparations have been used to immunise rats for subsequent production of monoclonal antibodies. By the further step of native polyacrylamide gel electrophoresis the semi-purified preparations yield homogeneous, dimeric (22-kilodalton, kDa) auxin-binding protein, which has been used to produce a polyclonal rabbit antiserum. The preliminary characterisation of this antiserum and of the five monoclonal antibodies is presented. Two of the monoclonal antibodies specifically recognise the major 22-kDa-binding protein polypeptide whilst the other three recognise, in addition, a minor 21-kDa species. All the monoclonal antibodies recognise the polypeptide rather than the glycan side chain and the polyclonal antiserum also recognises deglycosylated binding protein. The antibodies have been used to quantify the abundance of auxinbinding protein in a number of tissues of etiolated maize seedlings. Root membranes contain 20-fold less binding protein than coleoptile membranes.Abbreviations ABP auxin-binding protein - DEAE diethylaminoethyl - Ig immunoglobulin - kDa kilodalton - NAA naphthalene-1-acetic acid - M_r relative molecular mass - PAGE polyacrylamide gel electrophoresis - SDS sodium dodecyl sulfate     

Immunogold localization of acyl carrier protein in plants and Escherichia coli: Evidence for membrane association in plants

Immunogold labelling was used to study the distribution of acyl carrier protein (ACP) in Escherichia coli and a variety of plant tissues. In E. coli, ACP is distributed throughout the cytoplasm, confirming the observation of S. Jackowski et al. (1985, J. Bacteriol., 162, 5–8_. In the mesocarp of Avocado (Persea americana) and maturing seeds of oil-seed rape (Brassica napus cv. Jet Neuf), over 95% of the ACP is localised to plastids. The protein is almost exclusively located in the chloroplasts of leaf material from oil-seed rape. Approximately 80% of the gold particles associated with the ACP were further localized to the thylakoid membrane of the chloroplast. Since acetyl-CoA carboxylase has been reported to be localized to the thylakoid membrane (C.G. Kannangara and C.J. Jensen, 1975, Eur. J. Biochem., 54, 25–30), these results are consistent with the view that the two sequential enzymes in fatty-acid synthesis are in close spacial proximity.Abbreviations ACC acetyl CoA carboxylase - ACP acyl carrier protein - FAS fatty-acid synthetase     

Immunofluorescent and immunochemical evidence for the expression of cytovillin in the microvilli of a wide range of cultured human cells

We have previously purified a Mr 75,000 protein, cytovillin, from cultured human choriocarcinoma cells (JEG-3) and shown that this protein was specifically confined to the microvillus membrane of these cells. I have now studied the expression and the subcellular distribution of cytovillin in eighteen normal and transformed human cell lines and strains by using immunoblotting and indirect immunofluorescence microscopy. In all cell types, cytovillin was highly enriched in cell surface protrusions. When cell types were ranked according to their staining intensity, choriocarcinoma was highest, then amniotic epithelial cells, other choriocarcinoma cells and tumor cells, and finally fibroblastoid cells. The latter only gave faint diffuse fluorescence on the plasma membrane and, occasionally, on the microvilli. However, detergent extracts of all cell types could be shown to contain cytovillin by the use of immunoblotting techniques. Metabolic pulse-chase labelling experiments with JEG-3 cells demonstrated synthesis of cytovillin as a single-chain polypeptide. No precursor forms or specific proteolytic cleavage products could be seen either by immunoblotting or immunoprecipitation. The protein was found to be very stable with a biologic half-life of about 25 hours. The pI determined by isoelectric focusing was 6.1. These results were consistent with cytovillin being an integral component of the microvilli and other surface extensions of all human cell types examined.