The expression and intracellular distribution of phosphoglycerate kinase isoenzymes in Trypanosoma cruzi.

In this paper, we report the subcellular distribution of phosphoglycerate kinase (PGK) in epimastigotes of Trypanosoma cruzi. Approximately 80% of the PGK activity was found in the cytosol, 20% in the glycosomes. Western blot analysis suggested that two isoenzymes of 56 and 48 kDa, respectively, are responsible for the glycosomal PGK activity, whereas the cytosolic activity should be attributed to a single PGK of 48 kDa. In analogy to the situation previously reported for PGK in Trypanosoma brucei, these isoenzymes were called PGKA, C and B, respectively. However, in T. cruzi, PGKA seems not to be a minor enzyme like its counterpart in T. brucei. Whereas PGKC behaved as a soluble glycosomal matrix protein, PGKA appeared to be present at the inner surface of the organelle's membrane. After alkaline carbonate treatment, the enzyme remained associated with the particulate fraction of the organelles. Upon solubilization of glycosomes with Triton X-114, PGKA was recovered from the detergent phase, indicating its (partial) hydrophobic character and therefore, a possible hydrophobic interaction with the membrane. The PGKA gene was cloned and sequenced, but the predicted amino-acid sequence did not reveal an obvious clue as to the mechanism by which the enzyme is attached to the glycosomal membrane.

Lack of effect of chemokine receptor CCR2b gene polymorphism (64I) on HIV-1 plasma RNA viral load and immune activation among HIV-1 seropositive female workers in Abidjan, Côte d'Ivoire.

The prevalence of the CCR2b-V64I mutation among human immunodeficiency virus (HIV)-seropositive and -seronegative female workers and the potential effect of heterozygosity of this mutation on HIV-1 plasma RNA viral load and markers of immune activation were assessed. CCR2b-V64I was detected by polymerase chain reaction, followed by restriction enzymes analysis; plasma viral load was measured by the Amplicor HIV-1 monitor assay and CD4(+) T-cell counts and markers of immune activation by standard three-color FACscan flow cytometry. Of the 260 female workers, 56 (21.5%) were heterozygous for CCR2b-V64I, and 8 (3%) were homozygous. Of the 99 HIV-seronegative female workers, 19 (19.2%) were heterozygous for the CCR2b-V64I mutation compared with 37 (23%) of the 161 HIV-seropositive FSW (P = 0.47). In a univariate analysis of viral load among HIV-seropositive FSW, no difference was noted between those heterozygous for or without the mutation; both groups had plasma viral loads of 5.0 log(10) copies/ml. After controlling for the effects of CD4(+) T-cell counts in a multivariate analysis, no significant difference was observed between the groups in viral load or in markers of immune activation. The data suggest that the presence of the CCR2b mutation has no effect on HIV-1 plasma viral load and markers of immune activation in our study population. The finding that the frequency of this mutation is similar in HIV-seropositive and -seronegative female workers suggests that its presence is not associated with increased risk of HIV infection.

Molecular analysis of phosphoglycerate kinase in Trypanoplasma borreli and the evolution of this enzyme in kinetoplastida.

In the protozoan kinetoplastid organism Trypanoplasma borreli, phosphoglycerate kinase (PGK) activity was found in two different cell compartments: 80% in the cytosol and 20% in peroxisome-like organelles called glycosomes. However, only one functional pgk gene could be detected, in addition to a pseudo-pgk gene. No short-range linkage could be established between these two genes, although they are presumably present on the same chromosome. The intact gene codes for a polypeptide of 411 amino acids, with a C-terminal extension of four residues, -VAKF, a sequence with probably a low targeting efficiency for glycosomes. The calculated net charge and molecular mass of the encoded polypeptide are +13 and 44230Da, respectively. In other Kinetoplastida, different tandemly arranged genes code for distinct PGK isoenzymes in glycosomes and cytosol. By comparison of the pgk gene organization, and a phylogenetic analysis, we have traced a plausible scenario of the evolution of the PGK isoenzymes in these organisms and of the enzymes' intracellular compartmentation.

Organization, sequence and stage-specific expression of the phosphoglycerate kinase genes of Leishmania mexicana mexicana.

In Leishmania mexicana two genes were detected coding for different isoforms of the glycolytic enzyme phosphoglycerate kinase. This situation contrasts with that observed in other Trypanosomatidae (Trypanosoma brucei, Trypanosoma congolense, Crithidia fasciculata) analyzed previously, which all contain three different genes coding for isoenzymes A, B and C, respectively. All attempts to detect in L. mexicana a type A PGK, or a gene encoding it, proved unsuccesful. We have cloned and characterized the genes PGKB and PGKC. They code for polypeptides of 416 and 478 amino acids with a molecular mass of 45146 and 51318 Da, respectively. The two polypeptides are 99% identical. PGKC is characterized by a 62 residue C-terminal extension with alternating stretches of hydrophobic and charged, mainly positive amino acids. As in other Trypanosomatidae, PGKB is located in the cytosol, PGKC in the glycosomes. However, Leishmania mexicana distinguishes itself from other trypanosomatids by the simultaneous expression of these isoenzymes: approximately 80% of PGK activity is found in the cytosol and 20% in the glycosomes, both in promastigotes and in the amastigote-like form of the parasite.