Isolation and characterization of a chaperonin-60 gene of the human malaria parasite Plasmodium falciparum.

We report the isolation and sequence of genomic clones encoding a chaperonin 60 gene from the human malaria parasite Plasmodium falciparum. The gene contains a single intron of 868 nucleotides, the largest yet identified in this organism. The reading frame encodes a product with a predicted length of 719 amino acid residues (81.6 kDa), which is considerably longer than any chaperonin 60 protein sequenced to date, revealing good identity with other chaperonin 60 proteins. There is a putative mitochondrial signal peptide and an usually long carboxy terminus composed almost entirely of glutamic and aspartic acid residues. The gene was located on chromosome 12, and a 4-kb transcript was identified.

Plasmodium falciparum: analysis of chromosomes separated by contour-clamped homogenous electric fields.

We have established improved conditions for separating the chromosomes of Plasmodium falciparum by pulsed field gradient gel electrophoresis (PFG) using a contour-clamped homogenous electric field (CHEF) apparatus. Thirteen clearly separable chromosomal bands were reproducibly isolated from the strain FCR3 and their sizes have been determined. Evidence that indicates one band may contain two chromosomes is presented. The relationship between the PFG separable DNA and the number of unique chromosomes in P. falciparum is considered. We have established a relationship between the maximum resolvable sizes of the chromosomes and the pulse times. The chromosomal location of twenty-seven P. falciparum DNA probes is also reported.

Dihydrofolate reductase mutations and chromosomal changes associated with pyrimethamine resistance of Plasmodium falciparum.

The nucleotide sequence of the dihydrofolate reductase-thymidylate synthase (DHFR-TS) gene in pyrimethamine-resistant (PyrR) mutants of Plasmodium falciparum selected in vitro was examined to determine if specific mutations in DHFR were associated with drug resistance. We analysed the sequence of genomic DNA from strain FCR3, from eight previously isolated PyrR parasites derived from FCR3, and from strain Honduras-1. We found that: (1) five PyrR FCR3 mutants, FCR3-D4-D8, had an identical nucleotide change and a novel single amino acid change (Phe to Ser) at amino acid 223 of DHFR; (2) our originally reported nucleotide sequence of the DHFR-TS gene was of the PyrR strain Honduras-1, and was not of FCR3; (3) three PyrR mutants, FCR3-D1, D2, and D3, thought to have been derived from the FCR3 strain, were in fact isolates of Honduras-1. We also examined the chromosomal DNA of PyrR mutants by pulsed-field gradient gel (PFG) electrophoresis. The PyrR mutants FCR3-D1, D2, and D3 had several chromosome size polymorphisms compared to FCR3. In two of the PyrR FCR3 mutants, FCR3-D7 and D8, the chromosome 4-size DNA of FCR3 that the DHFR-TS probe normally hybridised to was not observed. Instead, in FCR3-D7, a chromosome larger than the chromosome 4-size DNA was observed to hybridise to the DHFR-TS probe. In FCR3-D8, two chromosomes that hybridised to the DHFR-TS probe were found. One of them was larger than FCR-3 chromosome 4-size DNA, and the other was smaller than FCR3 chromosome 1-size DNA.(ABSTRACT TRUNCATED AT 250 WORDS)

Formation of catenated colicin factor E1 deoxyribonucleic acid molecules in a recombination-deficient strain of Escherichia coli.

Catenated deoxyribonucleic acid molecules of colicin factor E1 (Col E1) were found with nearly equal frequency in minicells derived from Escherichia coli strain P678-54 recA(+) (Col E1) and P678-54 recA(-) (Col E1). The result suggests that the recombination function controlled by the recA gene does not influence the formation of catenated Col E1.

Physical and genetic mapping of the SPO2 prophage on the chromosome of Bacillus subtilis 168.

It has been found by density transfer and genetic mapping experiments that prophage SPO2 is linked to the antibiotic resistance marker ery-1 in Bacillus subtilis 168.