S. Taladriz et al., Cloning, molecular analysis and differential cell localisation of the p36 RACK analogue antigen from the parasite protozoon Crithidia fasciculata, FEBS LETTER, 443(3), 1999, pp. 375-380
The family of the RACK molecules (receptors for activated C kinases) are pr
esent in all the species studied so far. In the genus Leishmania, these mol
ecules also induce a strong immune reaction against the infection. We have
cloned and characterised the gene that encodes the RACK analogue from the p
arasite trypanosomatid Crithidia fasciculata (CACK), The molecule stems to
be encoded by two genes, The sequence analysis of the cloned open reading f
rame indicates the existence of a high degree of conservation not only with
other members of the Trypanosomatidae but also with mammalians. The study
of the protein kinase C phosphorylation sites shows the presence of three o
f them, shared with the mammalian species, additional to those present in t
he other protozoa suggesting a certain phylogenetic distance between the pr
otozoon Crithidia fasciculata and the rest of the Trypanosomatidae. The CAC
K-encoded polypeptide shows an additional sequence of four amino acids at t
he carboxy-terminal end,,which produces a different folding of the fragment
with the presence of an alpha-helix instead of the beta-sheet usual in all
the other species studied. A similar result is elicited at the amino-termi
nal end by the change of three amino acid residues, The immunolocalisation
experiments show that the CACK displays a pattern with a distribution mainl
y at the plasma membrane, different from that of the related leishmania spe
cies used as control, that displays a distribution close to the nucleus. Al
together, the data suggest that the existence of the structural differences
found may have functional consequences. (C) 1999 Federation of European Bi
ochemical Societies.