title: Identification of heat shock factor binding protein in Plasmodium falciparum.
abstract: BACKGROUND
  Heat shock factor binding protein (HSBP) was originally discovered in a yeast two-hybrid screen as an interacting partner of heat shock factor (HSF). It appears to be conserved in all eukaryotes studied so far, with yeast being the only exception. Cell biological analysis of HSBP in mammals suggests its role as a negative regulator of heat shock response as it appears to interact with HSF only during the recovery phase following exposure to heat stress. While the identification of HSF in the malaria parasite is still eluding biologists, this study for the first time, reports the presence of a homologue of HSBP in Plasmodium falciparum.
  
  
  METHODS
  PfHSBP was cloned and purified as his-tag fusion protein. CD (Circular dichroism) spectroscopy was performed to predict the secondary structure. Immunoblots and immunofluorescence approaches were used to study expression and localization of HSBP in P. falciparum. Cellular fractionation was performed to examine subcellular distribution of PfHSBP. Immunoprecipitation was carried out to identify HSBP interacting partner in P. falciparum.
  
  
  RESULTS
  PfHSBP is a conserved protein with a high helical content and has a propensity to form homo-oligomers. PfHSBP was cloned, expressed and purified. The in vivo protein expression profile shows maximal expression in trophozoites. The protein was found to exist in oligomeric form as trimer and hexamer. PfHSBP is predominantly localized in the parasite cytosol, however, upon heat shock, it translocates to the nucleus. This study also reports the interaction of PfHSBP with PfHSP70-1 in the cytoplasm of the parasite.
  
  
  CONCLUSIONS
  This study emphasizes the structural and biochemical conservation of PfHSBP with its mammalian counterpart and highlights its potential role in regulation of heat shock response in the malaria parasite. Analysis of HSBP may be an important step towards identification of the transcription factor regulating the heat shock response in P. falciparum.
authors.forename: Syed K
authors.initials: SK
authors.lastname: Sayeed
authors.forename: Varun
authors.initials: V
authors.lastname: Shah
authors.forename: Shweta
authors.initials: S
authors.lastname: Chaubey
authors.forename: Meetali
authors.initials: M
authors.lastname: Singh
authors.forename: Shuba V
authors.initials: SV
authors.lastname: Alampalli
authors.affiliation: Department of Biochemistry, Indian Institute of Science, Bangalore 560 012, India. tatu@biochem.iisc.ernet.in.
authors.forename: Utpal S
authors.initials: US
authors.lastname: Tatu
mesh_terms: D000595:Amino Acid Sequence; D002467:Cell Nucleus / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D006360:Heat-Shock Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D018869:Heat-Shock Response; D008969:Molecular Sequence Data; D010963:Plasmodium falciparum / Q000235:genetics / Q000502:physiology*; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D016415:Sequence Alignment
chemical_list: D006360:Heat-Shock Proteins