Recovery of DNA from agarose gels using liquid nitrogen.
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DNA↗
Biomedical subjects
M Koenen
Publications and source records attributed to M Koenen.
Nucleotide sequence of the rat muscle acetylcholine receptor epsilon-subunit.
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Amino Acid Sequence↗
Primary structure of the chicken c-mil protein:identification of domains shared with or absent from the retroviral v-mil protein.
The complete primary structure of the protein product of the proto-oncogene c-mil was deduced from the nucleotide sequence of chicken c-mil cDNA clones. The c-mil protein contains 647 amino acid residues and has a calculated molecular weight of 73,132. Based on sequence comparisons with proteins of known or presumed biochemical function, two domains were recognized on the c-mil protein. In the carboxyl-terminal half of the protein, a 250-amino acid segment displays significant homology to the protein kinase domains of the src oncogene protein or of protein kinase C. In the amino-terminal half, a cysteine-rich segment (Cys-X2-Cys-X9-Cys-X2-Cys-X7-Cys-X7-Cys) of the c-mil protein shares significant homology with two similar repetitive domains of protein kinase C. Of the two structural and presumably functional domains of the c-mil protein, only the kinase domain is contained within the carboxyl-terminal 379-amino acid polypeptide encoded by the transduced v-mil allele of avian oncogenic retrovirus MH2. Hence, truncation of the 5' coding region in the course of the transduction and the resulting lack of the authentic amino-terminal domain in the protein product of the transduced allele may be a critical event in changing mil function from physiologic to oncogenic.
Amino Acid Sequence↗
Characterisation of P. falciparum antigenic determinants isolated from a genomic expression library by differential antibody screening.
A genomic expression library of P.falciparum has been differentially screened with a number of immune sera. The response of 9 clones to the various sera is presented, together with the DNA sequence encoding the epitopes. All but one clone are extremely A+T rich and unlike the other P.falciparum epitopes described, are not composed of amino acid repeats. One clone, which responds specifically with a protective serum, has been analysed in detail. The epitope is carried on a 160kd antigen which is transcribed from a single gene to give a protein expressed in all of the erythrocytic forms. DNA sequence of this clone reveals it to have more than one open reading frame, only one of which is transcribed in the blood stages. The possible significance of the other open readings frames is discussed.
Amino Acid Sequence↗
72 residues of gal repressor fused to beta-galactosidase repress the gal operon of E. coli.
An active gene has been constructed which produces a chimera consisting of the N-terminal domain of the gal repressor and all but the first five residues of beta-galactosidase. Seventy two residues of gal repressor fused to beta-galactosidase as tetrameric core are sufficient to repress the gal operon in vivo and to bind to the gal operator in vitro.
Amino Acid Sequence↗
Immunoenzymatic detection of expressed gene fragments cloned in the lac Z gene of E. coli.
We describe a method which permits the detection of exon fragments. Such DNA was cloned and expressed in the promoter proximal part of the lac Z gene of Escherichia coli. The resulting antigen-beta-galactosidase chimeras are bound to their respective antibodies fixed to polyvinyl sheets. The beta-galactosidase part of the chimera permits detection of such clones by histochemical staining. As model DNA, we used the lac I gene cleaved with HaeIII, HhaI, or HpaII. Fragments were tailed with poly(dC) and inserted into the poly(dG)-tailed promoter proximal part of the lac Z gene. Recombinant clones, isolated on lactose-agar plates, were replica-plated and lysed with chloroform. Polyvinyl sheets coated with antibody against lac repressor were placed onto the top of the lysed colonies for immunoadsorption. The immune complexes were made visible after washing by incubation with 5-bromo-4-chloro-3-indolyl-beta-D-galactoside in buffered agar. The beta-galactosidase activity of the chimera cleaves the colourless histochemical compound to a blue dye at those positions where clones produce the antigen. In the case of the lac I gene two types of clones were isolated, carrying the NH2-terminal part of the lac repressor up to codons 27 and 75.
Amino Acid Sequence↗
Exon cloning: immunoenzymatic identification of exons of the chicken lysozyme gene.
A 10-kilobase DNA fragment containing exons 1 and 2 of the chicken lysozyme gene has been randomly cleaved with DNase I. After tailing and cloning into the plasmid pUK230, Lac+ colonies were selected. Colonies harboring expressed fragments of the exons could be detected by an immunoenzymatic assay using antibodies against lysozyme. The smallest fragment coded for 10 amino acids and the largest coded for almost all residues of exon 2. These results suggest that any gene of any genome cloned in this way can be detected if antibodies against the gene product are available.
Animals↗
pUR222, a vector for cloning and rapid chemical sequencing of DNA.
A multipurpose plasmid, pUR222, was constructed. It contains six unique cloning sites (PstI, SalI, AccI, HindII, BamHI and EcoRI) in a small region of its lac Z-gene part. Insertion of foreign DNA into the plasmid can be easily detected. Bacteria harbouring recombinant plasmids generally give rise to white colonies, while those containing only vector DNA form blue colonies on indicator plates. Plasmid DNA purified by a rapid method (Birnboim, H.C. and Doly, J. (1979) Nucl. Acids. Res. 7, 1513-1523) can be used for chemical sequencing of the cloned insert DNA. Labeled fragments need not be isolated after cutting with the proper restriction enzymes and are treated directly according to the sequencing protocol of Maxam and Gilbert.
Base Sequence↗
Human antisera detect a Plasmodium falciparum genomic clone encoding a nonapeptide repeat.
Plasmodium falciparum causes malaria infections in its human host. Its wide distribution in tropical countries is a major world health problem. Before a vaccine can be produced, the identification and characterization of parasite antigens is necessary. This can be achieved by the cloning and subsequent analysis of genes coding for parasite antigens. Recently established cDNA banks allow the expression of cDNA derived from the simian parasite Plasmodium knowlesi and P. falciparum in Escherichia coli. Recombinants encoding parasite antigens have been identified by immunodetection in both banks. Two of them contain repetitive units of 11 (ref. 7) or 12 (ref. 5) amino acids. We describe here the construction of an expression bank made directly from randomly generated fragments of P. falciparum genomic DNA. We detect several clones which react strongly with human African immune sera. One clone expresses an antigenic determinant composed of occasionally degenerated repeats of a peptide nonamer.
Amino Acid Sequence↗