John R. Preer

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Surface proteins from 11 antigenic types of Paramecium tetraurelia vary in molecular weight from 251,000 to 308,000. The size of a series of polyadenylated RNAs obtained from these types were correlated with the sizes of the proteins and judged to be the mRNAs for the proteins. The mRNAs were used to identify genomic DNA clones containing complementary(More)
Immobilization antigens of stock 51 of Paramecium tetraurelia were subjected to electrophoresis in NaDodSO(4)/polyacrylamide gels. Type A is estimated to have a molecular size of 300,000 daltons; H is estimated to be 288,000, D to be 280,000, E to be 270,000, B to be 253,000, and C to be 250,000. Poly(A)(+)RNAs have been isolated from cells producing these(More)
Paramecia of a given serotype express only one of several possible surface proteins called immobilization antigens (i-antigens). A 16-kilobase plasmid containing the gene for immobilization antigen A from Paramecium tetraurelia, stock 51, was injected into the macronucleus of deletion mutant d12, which lacks that gene. Approximately 40% of the injected(More)
Kappas (bacterial symbionts containing R bodies) have been studied in 16 strains of Paramecium aurelia, syngens 2 and 4. All produce toxins capable of killing sensitive paramecia. The first major class, the 51 group (consisting of the kappas of strains 51, 116, and 298), has R bodies which, when the pH is lowered below 6-5, unwind reversibly from the inside(More)
A method for the isolation of micronuclear DNA from Paramecium tetraurelia has been developed. After cell lysis, a low speed centrifugation at 1,000 g is used to remove all of the unbroken cells and macronuclei and approximately two thirds of the macronuclear fragments. Next a higher speed centrifugation of 9,000 g sediments the micronuclei and frees them(More)
The mutant Paramecium tetraurelia cell line d48 is unable to express the serotype A protein on its surface. Although the A gene is intact in the micronuclei of d48, the A gene copies in the macronucleus contain a large deletion eliminating virtually the entire coding sequence. Previous studies showed that microinjection of a plasmid containing the entire A(More)
The immobilization antigens (i-antigens) of Paramecium, large polypeptides of relative molecular mass approximately 300,000, are located on the cell surface. Each i-antigen is encoded by a different unlinked gene, and no more than one gene is expressed at a time. The proteins and the mRNAs and genes encoding them are readily isolated. Here we report the(More)
The macronuclear genes coding for rRNA (ribosomal DNA [rDNA]) of Paramecium tetraurelia, stock 51, are arranged in polymers consisting of units made up of a transcribed coding region and a nontranscribed spacer region. The whole macronuclear polymer ends with a portion of the spacer on either end followed by a telomere. Six kinds of macronuclear units, or(More)