Giardia lamblia expresses a proteobacterial-like DnaK homolog.
We identified a novel gene encoding molecular chaperone HSP70 in the amitochondriate parasite Giardia lamblia. The predicted protein is similar to bacterial DnaK and mitochondrial HSP70s. The gene is transcribed and translated at a constant level during trophozoite growth and encystation. Alignment of the sequence with a data set of cytosolic, endoplasmic reticulum (ER), mitochondrial, and DnaK HSP70 homologs indicated that the sequence was extremely divergent and contained insertions unique to giardial HSP70s. Phylogenetic analyses demonstrated that this sequence was distinct from the cytosolic and ER forms and was most similar to proteobacterial and mitochondrial DnaKs. However, a specific relationship with the alpha proteobacterial and mitochondrial sequences was not strongly supported by phylogenetic analyses of this data set, in contrast to similar analyses of cpn60. These data neither confirm nor reject the possibility that this gene is a relic of secondary mitochondrial loss; they leave open the possibility that it was acquired in a separate endosymbiotic event.
The Josephine Bay Paul Center of Comparative Molecular Biology and Evolution, Marine Biological Laboratory, Woods Hole, Massachusetts 02543-1015, USA.
H G
HG
Morrison
A J
AJ
Roger
T G
TG
Nystul
F D
FD
Gillin
M L
ML
Sogin
D000595:Amino Acid Sequence; D000818:Animals; D015152:Blotting, Northern; D015153:Blotting, Western; D029968:Escherichia coli Proteins; D017125:Genes, Protozoan; D016829:Giardia lamblia / Q000235:genetics* / Q000502:physiology; D018840:HSP70 Heat-Shock Proteins / Q000145:classification / Q000235:genetics* / Q000378:metabolism; D006358:Hot Temperature; D006801:Humans; D008969:Molecular Sequence Data; D018384:Oxidative Stress; D010100:Oxygen / Q000378:metabolism; D010802:Phylogeny; D015800:Protozoan Proteins / Q000235:genetics* / Q000378:metabolism; D016053:RNA, Protozoan / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment
D029968:Escherichia coli Proteins; D018840:HSP70 Heat-Shock Proteins; D015800:Protozoan Proteins; D016053:RNA, Protozoan; C063842:dnaK protein, E coli; D010100:Oxygen