Two-dimensional electrophoresis of proteins discriminates aphid clones of Sitobion avenae differing in BYDV-PAV transmission.

Aset of 39 F1 Sitobion avenae clones was obtained by selfing a poorly efficient BYDV-PAV vector clone. These clones were genetically typed by 11 microsatellite loci, and tested for BYDV-PAV4 transmission to barley. The 39 clones displayed a continuum in transmission percentages, from 0% to 88% with a significant clone effect. From this set, two highly efficient (HEV) and two poorly efficient (PEV) vectoring clones were more precisely characterized for transmission of two other PAV isolates. The molecular bases of the lower transmissibility of BYDV-PAV4 by PEV clones and of the aphid vectoring properties were investigated respectively by comparing the sequences corresponding to structural proteins (CP and RTD) of BYDV, and by using proteomic analysis of aphids in two dimensional electrophoresis (2-DE) with immobilized pH gradients (IPG) after an improved protein extraction. Four residues specific to BYDV-PAV4 located in the CP sequence (A(24) and L(130)) or in the RTD region (M(334) and S(456)) could be responsible for the lower transmissibility of this isolate by PEV clones. Among a total of 2150 well-resoluted spots scored on S. avenae proteinic pattern, only twelve proteins were qualitatively or quantitatively different between clones. Four out of them discriminated HEV and PEV groups.

A comparison between Sypro Ruby and ruthenium II tris (bathophenanthroline disulfonate) as fluorescent stains for protein detection in gels.

A comparison between two fluorescent metal chelates for staining proteins separated by electrophoresis has been carried out. One of these chelates is ruthenium II tris (bathophenanthroline disulfonate) and the other is commercial Sypro Ruby. Both can be efficiently detected either with UV tables or with commercial laser fluorescence scanners. The sensitivity and homogeneity of the stains and the interference with mass spectrometry analysis have been investigated. It appears that both stains perform similarly for protein detection, while ruthenium II tris (bathophenanthroline disulfonate) performs better for mass spectrometry analyses and as cost-effectiveness ratio. However, Sypro Ruby is easier to use as a stain.

Comparison of the PR mutant with the wild-type strain of proteus mirabilis brings insight into peroxide resistance factors and regulation of catalase expression.

The peroxide resistant mutant (PR) of Proteus mirabilis was characterized by an increased constitutive catalase activity concomitant with a large production of specific mRNA. Survival toward hydrogen peroxide during exponential phase was increased by H2O2 pretreatment in the wild type but not in the mutant, although the catalase of both strains was not inducible under these conditions. In the mutant, besides catalase, over-produced proteins comprised two different alkyl hydroperoxide reductase subunit C (AhpC) proteins and a protein homologous to the stationary phase transcription factor SspA of Escherichia coli. Conversely, the flagellin A (FlaA) of P. mirabilis was repressed in the PR mutant. Genomic DNA fragments of 2.9 kb carrying the catalase gene (katA) together with the 5' and 3' flanking regions were isolated from both strains and found to be identical. Upstream of katA, a Fur box-like sequence was found, but surprisingly, restricting iron in the culture medium caused a decrease in catalase production. The PR mutant presents similarities with other peroxide resistant mutants, but the regulation of catalase biosynthesis in P. mirabilis seems somewhat different from other close species such as E. coli.

Gene induction during differentiation of human monocytes into dendritic cells: an integrated study at the RNA and protein levels.

Changes in gene expression occurring during differentiation of human monocytes into dendritic cells were studied at the RNA and protein levels. These studies showed the induction of several gene classes corresponding to various biological functions. These functions encompass antigen processing and presentation, cytoskeleton, cell signalling and signal transduction, but also an increase in mitochondrial function and in the protein synthesis machinery, including some, but not all, chaperones. These changes put in perspective the events occurring during this differentiation process. On a more technical point, it appears that the studies carried out at the RNA and protein levels are highly complementary.

Towards a human repertoire of monocytic lysosomal proteins.

The lysosomal compartment of human monocytic cells has never been investigated by a proteomic approach. By a combination of one-dimensional (1-D) and two-dimensional (2-D) gel electrophoresis, protein identification by N-terminal sequencing, matrix assisted laser desorption/ionization-mass spectrometry (MALDI-MS) peptide mass fingerprinting and tandem mass spectrometry (MS/MS) peptide sequence analysis, we initiated an exhaustive study of the human lyososomal proteome, which aims at establishing a 2-D reference map of human soluble lyososomal proteins. Human monocytic U937 cells were induced to secrete lysosomal soluble hydrolases by addition of NH4Cl in the culture medium. Since lysosomal soluble proteins are characterized by the presence of mannose-6-phosphate, they were purified on an affinity support bearing mannose-6-phosphate receptor. Analysis of the purified fraction led to the preliminary identification of fifteen proteins, among which twelve are well-known lysosomal hydrolases, one is assumed to be lysosomal on the basis of sequence homology to cysteine proteinases of the papain family, and two (leukocystatin and the human cellular repressor of E1A-stimulated genes) are described here for the first time as mannose-6-phosphate-containing proteins.

Analysis of membrane proteins by two-dimensional electrophoresis: comparison of the proteins extracted from normal or Plasmodium falciparum-infected erythrocyte ghosts.

Parasite-encoded membrane proteins translocated to the surface of infected erythrocytes or in specialized vesicles underneath (Maurer's clefts) play a key role in the asexual life cycle of Plasmodium falciparum (a malaria-causing protozoan), by mediating key steps such as red blood cell invasion, sequestration of infected cells in microcapillaries, and red blood cell rupture. A large-scale analysis of these membrane proteins would therefore be of great help to gain knowledge of the different stages of the Plasmodium falciparum life cycle. In order to be able to detect and identify parasite-encoded proteins directed to the red blood cell membrane, we first defined the conditions required for optimal extraction and separation of normal red blood cell ghost proteins by two-dimensional gel electrophoresis. These conditions included the use of urea, thiourea and new zwitterionic detergents in the extraction and isoelectric focusing media. The optimized conditions were then applied to analyze normal and P. falciparum-infected red blood cell ghosts. Several protein spots were found only in infected ghosts and are expected to represent parasite-encoded proteins. These proteins are currently under investigation.