M. Chaudhuri, Cloning and characterization of a novel serine/threonine protein phosphatase type 5 from Trypanosoma brucei, GENE, 266(1-2), 2001, pp. 1-13
Reversible protein phosphorylation is essential for the regulation of numer
ous cellular functions and differentiation. The haemo-flagellated parasitic
protozoan Trypanosoma brucei, the causative agent for Africa trypanosomias
is undergoes various stages of cellular differentiation during its digeneti
c life cycle. A complete cDNA of a unique serine/threonine phosphatase: typ
e five (TbPP5) was cloned and characterized from T. brucei. TbPPS contains
an open reading frame of 1416 bp that encodes a protein of about 53 kDa and
exists as a single copy gene in the T. brucei genome. The deduced amino ac
id sequence showed 45-48% overall identity and 60-65% similarity with prote
in phosphatase 5 's (PP5) from different species. Analysis of the primary s
equence revealed that TbPPS contains three TPR motifs at the N-terminal reg
ion (amino acid residues 7-107) while the phosphatase catalytic domain occu
rs in the C-terminal region (amino acid residues 210-410). A TbPPS cDNA hyb
ridized with a transcript of 2.5 kb which is present at similar levels in t
he procyclic and the bloodstream forms. However, the level of expression of
the TbPPS protein (52 kDa) detected by an antibody developed against a rec
ombinant protein produced in E. coli was about 2-fold higher in the procycl
ic than the bloodstream form. The TbPP5 transcript level gradually decrease
d in cells grown in the logarithmic phase to the stationary phase in cultur
e. Moreover, 18 h serum starvation of the procyclic forms decreased the lev
el of the specific transcript about 3-fold suggesting that this: protein ma
y play a role during the active growth phase of the organism. The recombina
nt protein showed phosphatase activity which was stimulated about 2.6-fold
by arachidonic acid with half-maximal activity at 75 muM Indirect immuno-fl
uoresence of permeabilized cells revealed that the protein is localized in
the cytosol and the nucleus This is the first report for the identification
of a type 5 serine/threonine protein phosphatase in an ancient eukaryote s
uch as T. brucei. (C) 2001 Elsevier Science B.V. All rights reserved.