Characterisation of PfSec61, a Plasmodium falciparum homologue of a component of the translocation machinery at the endoplasmic reticulum membrane of eukaryotic cells.
Plasmodium falciparum secretes several proteins that cause changes in the erythrocyte membrane enabling it to survive within red blood cells. Little is known of the mechanisms involved in the secretion and targeting of parasite polypeptides to the various cell compartments. The P. falciparum gene homologous to the mammalian Sec61alpha, gene, which encodes a component of the translocation pore in the endoplasmic reticulum of eukaryotic cells, was characterised to investigate the translocation process in the parasite. PfSec61 is present as a unique copy in the parasite genome and was mapped to chromosome 13. It encodes a 40 kDa polypeptide, as shown by immunoblotting and immunoprecipitation of [35S]methionine metabolically-labelled parasite extracts. The deduced amino acid sequence of PfSec61 is 87% similar to the mammalian polypeptide, and the two proteins give similar hydropathy plots. These results strongly suggest that PfSec61 has the same topological orientation and functional role as Sec61alpha. Anti-PfSec61 antibodies were used to investigate the cellular location and kinetics of expression of the polypeptide in the parasite. Immunofluorescence confocal microscopy showed that PfSec61 was located in the parasite cytoplasm, close to the nucleus, in a position consistent with its being in the endoplasmic reticulum.
Couffin
S
S
Unité de Parasitologie Expérimentale, URA 1960, Institut Pasteur, Paris, France.
Hernandez-Rivas
R
R
Blisnick
T
T
Mattei
D
D
D000595:Amino Acid Sequence; D000818:Animals; D001692:Biological Transport; D015139:Blotting, Southern; D002451:Cell Compartmentation; D002874:Chromosome Mapping; D003001:Cloning, Molecular; D018076:DNA, Complementary; D016054:DNA, Protozoan / Q000235:genetics; D004721:Endoplasmic Reticulum / Q000378:metabolism; D005057:Eukaryotic Cells; D017125:Genes, Protozoan; D008565:Membrane Proteins / Q000235:genetics*; D008969:Molecular Sequence Data; D010963:Plasmodium falciparum / Q000235:genetics*; D016133:Polymerase Chain Reaction; D015800:Protozoan Proteins / Q000235:genetics*; D000069816:SEC Translocation Channels; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid
D018076:DNA, Complementary; D016054:DNA, Protozoan; D008565:Membrane Proteins; D015800:Protozoan Proteins; D000069816:SEC Translocation Channels