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Pfmrk, a MO15-related protein kinase from Plasmodium falciparum. Gene cloning, sequence, stage-specific expression
1Department of Medical Parasitology, London School of Hygiene and Tropical Medicine, UK.
Abstract:
Cyclin-dependent kinases (Cdks) play a central role in the regulation of the eukaryotic cell cycle. A novel gene encoding a Cdk-like protein, Pfmrk, has been isolated from the human malaria parasite Plasmodium falciparum. The gene has no introns and comprises an open reading frame encoding a protein of 324 amino acids with a predicted molecular mass of 38 kDa. Database searches revealed a striking similarity to the Cdk subfamily with the highest similarity to human MO15 (Cdk7). The overall sequence of Pfmrk shares 62% similarity and 46% identity with human MO15, in comparison to the 49-58% similarity and 34-43% identity with other human Cdks. Pfmrk contains two unique inserts: one consisting of 5 amino acids just before the cyclin-binding motif and the other composed of 13 amino acids within the T-loop equivalent region. Southern blots of genomic DNA digests and chromosomal separations showed that Pfmrk is a single-copy gene conserved between several parasite strains and is located on chromosome 10. A 2500-nucleotide transcript of this gene is expressed predominantly in the sexual blood stages (gametocytes), suggesting that Pfmrk may be involved in sexual stage development.
Insights
A novel gene, Pfmrk, encoding a cyclin-dependent kinase (Cdk)-like protein was identified in the malaria parasite Plasmodium falciparum. This gene is predominantly expressed in gametocytes, suggesting a role in sexual stage development.
Area of Science:
- Molecular biology
- Parasitology
- Cell cycle regulation
Background:
- Cyclin-dependent kinases (Cdks) are crucial regulators of the eukaryotic cell cycle.
- The malaria parasite Plasmodium falciparum requires specific regulatory mechanisms for its complex life cycle.
Purpose of the Study:
- To identify and characterize novel Cdk-like genes in Plasmodium falciparum.
- To investigate the potential role of Pfmrk in parasite development.
Main Methods:
- Gene isolation and sequencing of Pfmrk from Plasmodium falciparum.
- Bioinformatic analysis to compare Pfmrk sequence with known Cdks.
- Southern blotting to determine gene copy number and conservation.
- Northern blotting to analyze gene expression patterns.
Main Results:
- A novel gene, Pfmrk, encoding a 38 kDa Cdk-like protein was isolated.
- Pfmrk shows highest similarity to human MO15 (Cdk7) among known Cdks.
- Pfmrk is a single-copy gene located on chromosome 10 and conserved across parasite strains.
- A 2500-nucleotide transcript of Pfmrk is mainly expressed in gametocytes.
Conclusions:
- Pfmrk represents a Plasmodium falciparum homolog of Cdk7.
- The unique inserts in Pfmrk may confer specific functions.
- Pfmrk's predominant expression in gametocytes suggests a role in sexual stage development in malaria parasites.