A point mutation in an unusual Sec7 domain is linked to brefeldin A resistance in a Plasmodium falciparum line generated by drug selection.
The malaria parasite Plasmodium falciparum has an unusual organization of its secretory compartments. As an approach to a functional identification of auxiliary proteins involved in secretion, a parasite line was generated by drug selection that is resistant to brefeldin A, an inhibitor of the secretory pathway. In the resistant line, neither protein secretion nor parasite viability were affected by the drug. The analysis of a sec7 domain, a conserved structure of guanine nucleotide exchange factors (ARF-GEF) required for the activation of ADP-ribosylation factors, revealed a single methionine-isoleucine substitution in the resistant parasite line. ARF-GEFs are key molecules in the formation of transport vesicles and the main targets of brefeldin A. The methionine residue in this position of sec7 domains is highly conserved and confers brefeldin A sensitivity. Unlike other eukaryotes that have multiple ARF-GEFs, the plasmodial genome encodes a single sec7 domain. This domain shows a distinct structural difference to all sec7 domains analysed so far; two conserved subdomains that are essential for protein function are separated in the plasmodial protein by an insertion of 146 amino acids.
Baumgartner
F
F
Fachbereich Biologie, Philipps-Universität Marburg, 35032 Marburg, Germany.
Wiek
S
S
Paprotka
K
K
Zauner
S
S
Lingelbach
K
K
D020727:ADP-Ribosylation Factors / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D020126:Brefeldin A / Q000494:pharmacology*; D004351:Drug Resistance; D004912:Erythrocytes / Q000469:parasitology; D020662:Guanine Nucleotide Exchange Factors / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D006801:Humans; D018942:Macrolides; D016778:Malaria, Falciparum; D008969:Molecular Sequence Data; D021261:Parasitic Sensitivity Tests; D010963:Plasmodium falciparum / Q000187:drug effects* / Q000235:genetics / Q000254:growth & development; D017354:Point Mutation; D017434:Protein Structure, Tertiary; D017422:Sequence Analysis, DNA
D000900:Anti-Bacterial Agents; D020662:Guanine Nucleotide Exchange Factors; D018942:Macrolides; D020126:Brefeldin A; D020727:ADP-Ribosylation Factors