The [FeFe] hydrogenase of Nyctotherus ovalis has a chimeric origin

Background

The hydrogenosomes of the anaerobic ciliate Nyctotherus ovalis show how mitochondria can evolve into hydrogenosomes because they possess a mitochondrial genome and parts of an electron-transport chain on the one hand, and a hydrogenase on the other hand. The hydrogenase permits direct reoxidation of NADH because it consists of a [FeFe] hydrogenase module that is fused to two modules, which are homologous to the 24 kDa and the 51 kDa subunits of a mitochondrial complex I.

Results

The [FeFe] hydrogenase belongs to a clade of hydrogenases that are different from well-known eukaryotic hydrogenases. The 24 kDa and the 51 kDa modules are most closely related to homologous modules that function in bacterial [NiFe] hydrogenases. Paralogous, mitochondrial 24 kDa and 51 kDa modules function in the mitochondrial complex I in N. ovalis. The different hydrogenase modules have been fused to form a polyprotein that is targeted into the hydrogenosome.

Conclusion

The hydrogenase and their associated modules have most likely been acquired by independent lateral gene transfer from different sources. This scenario for a concerted lateral gene transfer is in agreement with the evolution of the hydrogenosome from a genuine ciliate mitochondrion by evolutionary tinkering.     

Phylogenetic analysis of the outer-membrane-protein genes of Chlamydiae, and its implication for vaccine development

Examination of 18 complete and 6 partial sequences of the major outer- membrane protein from 24 chlamydiae isolates was used to reconstruct their evolutionary relationships. From this analysis, assuming that the clades with 100% bootstrap support are correct, come the following conclusions: (1) The tree of these sequences is not congruent with the phylogeny of the hosts, and thus host switching would seem to have occurred, thereby limiting the extent to which there has been coevolution of parasite and host. (2) The tree is also noncongruent with clustering by type of cell infected, thereby limiting the extent to which there has been coevolution of parasite and the cell type that it infects. (3) The tree is also noncongruent with clustering by the organ infected (eyes or genitalia), thereby limiting the extent to which there has been coevolution of parasite and the organ that it infects. (4) The tree is also noncongruent with genital strains arising from lymphogranuloma venereum strains. (5) The tree is also noncongruent with the geographic site at which the isolates were obtained, thereby limiting the extent of divergence explained by geographic separation. (6) There are estimated to be 185 amino acid positions that are invariable (as opposed to unvaried) in the major outer-membrane protein. There are 10 unvaried positions in the variable domains, of which 9 appear to be invariable, giving some reason to hope that development of a vaccine might be possible. (7) The rate of change of this protein is too small to see increased divergence over the time span of isolation of these genes, giving hope to any vaccine having longevity. Bootstrapping supports those portions of the tree on which the first five conclusions above depend. The picture that these results provide is more one of pathogen versatility than one of coevolutionary constraints. In addition, we examined 10 60-KDa, outer-membrane protein- 2 genes, all but one of which were from these same strains. The tree was not, among the trachomatis strains, congruent with the major-outer- membrane protein tree, suggesting that gene exchange could be occurring among strains. Moreover, there is an apparent slowdown in divergence in this gene, among the trachomatis strains.      

The properties of a rat serum protein labelled by the injection of sodium selenite

Properties of a serum selenoprotein which was labelled after the injection of low levels of ⁷⁵SeO₃^2? to rats on a selenium-adequate diet were investigated. When serum was collected three hours after injection the label was incorporated preferentially into one major serum fraction as shown by polyacrylamide gel electrophoresis. Binding was strong, a demonstrated by the fact that very little label was removed by dialysis against 0.60 M NaCl or 0.50 M β-mercapto-ethanol; however, 80% of the ⁷⁵Se was removed by dialysis against 0.50 M NaOH.Molecular weight studies by sodium dodecyl sulfate polyacrylamide gel elecphoresis gave a subunit size of 49 000 under most conditions; when exposed to high concentrations of the detergent (2%) some ⁷⁵Se was associated with a protein having a molecular weight of 25 000. The native selenoprotein eluted before serum albumin on Sephadex G-150 indicating a molecular weight greater than 67 000. The selenoprotein did not coelute with glutathione peroxidase on DEAE-Sephadex A-50.The prior administration of actinomycin D and cycloheximide resulted in a reduction in incorporation of ²⁷Se into serum by 46% and 70%, respectively, which is consistent with the hypothesis that ⁷⁵Se is going into newly synthesized protein. The isoelectric point was determined to be 5.4; when heparin was present, the pI was lowered to 3.2. Treatment with 2 M NaCl did not dissociate the protein · heparin complex, while exposure to 0.25 M β-mercaptoethanol resulted in the dissociation of 60% of the complex.The fact that selenium is so tigthly associated with one serum protein when administered at levels that would be considered normal under most nutritional conditions suggests an important role for this protein, perhaps in the transport of this essential micronutrient throughout the body.     

Use of cervicovaginal fluid for the identification of biomarkers for pathologies of the female genital tract

Cervicovaginal fluid has an important function in the homeostasis and immunity of the lower female genital tract. Analysis of the cervicovaginal fluid proteome may therefore yield important information about the pathogenesis of numerous gynecological pathologies. Additionally, cervicovaginal fluid has great potential as a source of biomarkers for these conditions.