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Query: UMLS:C0026936 (Mycoplasma)
 14,761 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Mycoplasma virus MV-Lg-pS2-L172 was sensitive to heat (56 degrees C/30 minutes), Nonidet-P40 and ether. In these respects it resembled Plasmavirus MB-L2. However, it differed from MV-L2 (and the other mycoplasma viruses, MV-L1, MV-L3 and BN1 virus) in reciprocal plaque inhibition and serum neutralization tests (MV-L2 only). By plaque formation on host lawns resistant to the different mycoplasma viruses, including MV-Lg-pS2-L172, this latter virus was shown to be distinct from the other viruses, including MV-L2. Both MV-Lg-pS2-L172 and MV-L2 possessed one polypeptide band (out of 10) that was not common to the heterologous virus.
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PMID:Comparison of mycoplasmatales virus MV-Lg-pS2-L172 with plasmavirus MV-L2 and the other mycoplasma viruses. 51 4

Recently, we reported the purification to homogeneity and characterization of Ca(2+)- and Mg(2+)-dependent endonuclease P40 produced by Mycoplasma penetrans (M. Bendjennat, A. Blanchard, M. Loutfi, L. Montagnier, and E. Bahraoui, J. Bacteriol. 179; 2210-2220, 1997), a mycoplasma which was isolated for the first time from the urine of human immunodeficiency virus-infected patients. To evaluate how this nuclease could interact with host cells, we tested its effect on CEM and Molt-4 lymphocytic cell lines and on peripheral blood mononuclear cells. We observed that 10(-7) to 10(-9) M P40 is able to mediate a cytotoxic effect. We found that 100% of cells were killed after 24 h of incubation with 10(-7) M P40 while only 40% cytotoxicity was obtained after 72 h of incubation with 10(-9) M P40. Phase-contrast microscopy observations of P40-treated cells revealed morphological changes, including pronounced blebbing of the plasma membrane and cytoplasmic shrinkage characteristic of programmed cell death, which is in agreement with the internucleosomal fragmentation of P40-treated cell DNA as shown by agarose gel electrophoresis. We showed that (125)I-radiolabeled or fluorescein isothiocyanate-labeled P40 was able to bind specifically in a dose-dependent manner to the cell membrane of CEM cells, which suggested that the cytotoxicity of P40 endonuclease was mediated by its interaction with the cell surface receptor(s). The concentration of unlabeled P40 required to inhibit by 50% the formation of (125)I-P40-CEM complexes was about 3 x 10(-9) M, indicating a high-affinity interaction. Both P40 interaction and cytotoxicity are Ca(2+) dependent. Our results suggest that the cytotoxicity of M. penetrans observed in vitro is mediated at least partially by secreted P40, which, after interaction with host cells, can induce an apoptosis-like death. These results strongly suggest a major role of mycoplasmal nucleases as potential pathogenic determinants.
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PMID:Role of Mycoplasma penetrans endonuclease P40 as a potential pathogenic determinant. 1045 86

A method was developed for protein localization in Mycoplasma pneumoniae by immunofluorescence microscopy. The P1 adhesin protein was revealed to be located at least at one cell pole in all adhesive cells, as has been observed by immunoelectron microscopy. Cell images were classified according to P1 localization and assigned by DNA content. Cells with a single P1 focus at one cell pole had a lower DNA content than cells with two foci, at least one of which was positioned at a cell pole. Those with one focus at each cell pole had the highest DNA content, suggesting that the nascent attachment organelle is formed next to the old one and migrates to the opposite cell pole before cell division. Double staining revealed that the accessory proteins for cytadherence-HMW1, HMW3, P30, P90, P40, and P65-colocalized with the P1 adhesin in all cells. The localization of cytadherence proteins was also examined in cytadherence-deficient mutant cells with a branched morphology. In M5 mutant cells, which lack the P90 and P40 proteins, HMW1, HMW3, P1, and P30 were focused at the cell poles of short branches, and P65 showed no signal. In M7 mutant cells, which produce a truncated P30 protein, HMW1, HMW3, P1, P90, and P40 were focused, and P65 showed no signal. In M6 mutant cells, which express no HMW1 and a truncated P30 protein, the P1 adhesin was distributed throughout the entire cell body, and no signal was detected for the other proteins. These results suggest that the cytadherence proteins are sequentially assembled to the attachment organelle with HMW1 first, HMW3, P1, P30, P90, and P40 next, and P65 last.
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PMID:Visualization of the attachment organelle and cytadherence proteins of Mycoplasma pneumoniae by immunofluorescence microscopy. 1116 93

An immunodominant protein, P40, of Mycoplasma agalactiae was analyzed genetically and functionally. The gene encoding P40 was cloned from type strain PG2, sequenced, submitted to point mutagenesis in order to convert mycoplasma-specific TGA(Trp) codon to the universal TGG(Trp) codon, and subsequently expressed in Escherichia coli. Nucleotide sequence-derived amino acid sequence comparisons revealed a similarity of P40 to the adhesin P50 of Mycoplasma hominis and to protein P89 of Spiroplasma citri, which is expected to be involved in adhesion. The amino acid sequence of P40 revealed a recognition site for a signal peptidase and strong antigenic and hydrophilic motifs in the C-terminal domain. Triton X-114 phase partitioning confirmed that P40 is a membrane protein. Fab fragments of antibodies directed against recombinant purified P40 significantly inhibited adherence of M. agalactiae strains PG2 to lamb joint synovial cells LSM 192. Sera taken sequentially from sheep infected with PG2 revealed that P40 induced a strong and persistent immune response that gave strong signals on immunoblots containing recombinant P40 even 3 months after infection. The gene encoding P40 was present in a single copy in all of the 26 field strains of M. agalactiae analyzed and was not detected in closely related mycoplasma species. P40 was expressed as a protein with an apparent molecular mass of 37 kDa on sodium dodecyl sulfate-acrylamide gels by all M. agalactiae strains except for serotype C strains, which showed nonsense mutations in their p40 genes.
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PMID:Characterization of P40, a cytadhesin of Mycoplasma agalactiae. 1222 89

Cytadherence proteins of Mycoplasma pneumoniae are localized at the attachment organelle, which is involved in adhesion, gliding motility, and cell division. The localization of these proteins in cytadherence-deficient mutants was examined by immunofluorescence microscopy. In the class I-2 mutant, which has a frameshift mutation in the hmw2 gene, fluorescent foci for HMW1 and HMW3 were found with reduced intensity, and P1 adhesin showed reduced focusing. However, foci for P90, P40, P30, and P65 were not observed in this mutant. In the class IV-22 mutant, which lacks expression of P1, P90, and P40, the other cytadherence proteins (HMW1, HMW3, P30, and P65) were focused. In a mutant lacking HMW1, signals for HMW3, P90, P40, P30, and P65 were not found, and P1 was distributed throughout the cell. These results suggest that HMW1 is essential for the localization of all other cytadherence proteins, while HMW2 is essential for the localization of P90, P40, P30, and P65. The electron-dense core in cytadherence mutants was observed by thin-section electron microscopy, suggesting that its formation depends on HMW1 and HMW2 and that P1 localization occurs independent of the formation of the electron-dense core. Doubly stained preparations visualized by immunofluorescence microscopy showed that the P1 adhesin, P90, and P40 colocalized to a subregion of the attachment organelle in the wild-type strain. HMW1 and HMW3 also colocalized to a different subregion of the attachment organelle, while P30 and P65 localized at more distal ends of cell poles than HMW1 and HMW3. These differences were more pronounced in cytadherence mutants. These results suggest that there are three distinct subcellular protein localization sites in the attachment organelle, which were represented by HMW1-HMW3, P1-P90-P40, and P30-P65.
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PMID:Attachment organelle formation represented by localization of cytadherence proteins and formation of the electron-dense core in wild-type and mutant strains of Mycoplasma pneumoniae. 1253 84

Mycoplasma membrane proteins are generally designated according to their apparent molecular weight measured by SDS-PAGE. Several results about mycoplasma membrane antigens are conflicting because some doubts are emerging about the accuracy of the method utilised to identify the antigens. Aim of this work, was to characterise proteins separated after sodium dodecylsulfate polyacrylamide gel electrophoresis (SDS-PAGE)-mass spectrometry to allow an uncontroversial designation of the antigens. Fifteen proteins with molecular weights ranging from 15,000 to 80,000 Da had been excised from gel and their whole molecular weight and proteolytic pattern had been determined using MALDI-TOF. The peptide pattern obtained using trypsin digestion allowed us to identify LipA, P48, P59, P80 and P40. Some other proteins showed analogies to proteins of Mycoplasma genitalium or Mycoplasma pneumoniae the only Mycoplasmas completely sequenced. There wasn't a close correspondence between the SDS-PAGE apparent molecular weight (generally used to name the proteins), the gene derived calculated mass and the molecular weight of whole proteins measured by MALDI-TOF. Only micro sequence data obtained by MS/MS allowed us to identify LipC, described as one of the most important Mycoplasma agalactiae antigens. This protein was found in correspondence with the 50 kDa region, instead of the 25 kDa region, confirming a phenomenon that we previously described.
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PMID:Characterization of sodium dodecylsulfate polyacrylamide gel electrophoresis-separated M. agalactiae membrane antigens by mass spectrometry. 1518

A mutation in gene MPN142 (orf6) was identified in the Mycoplasma pneumoniae cytadherence mutant III-4. MPN142 encodes virulence-specific proteins P90 and P40 (proteins B and C, respectively). Analysis of MPN142 in a cytadhering revertant and complementation using a recombinant wild-type allele confirmed the role of this mutation in the cytadherence defect.
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PMID:Identification and complementation of a mutation associated with loss of Mycoplasma pneumoniae virulence-specific proteins B and C. 1562 45

Although the annotation of the complete genome sequence of Mycoplasma pneumoniae did not reveal a bacterial type I signal peptidase (SPase I) we showed experimentally that such an activity must exist in this bacterium, by determining the N-terminus of the N-terminal gene product P40 of MPN142, formerly called ORF6 gene. Combining mass spectrometry with a method for sulfonating specifically the free amino terminal group of proteins, the cleavage site for a typical signal peptide was located between amino acids 25 and 26 of the P40 precursor protein. The experimental results were in agreement with the cleavage site predicted by computational methods providing experimental confirmation for these theoretical analyses.
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PMID:Experimental proof for a signal peptidase I like activity in Mycoplasma pneumoniae, but absence of a gene encoding a conserved bacterial type I SPase. 1594 20

The genes MPN141 and MPN142 encode the major adhesin P1 and the cytadherence-related B/C proteins (P90/P40), respectively, in Mycoplasma pneumoniae. Using reverse transcriptase PCR we found open reading frames MPN140 to MPN142 constitute a polycistronic transcriptional unit. Cytadherence mutant IV-22 has a frameshift mutation in MPN141 and lacks the P1, B, or C proteins. Recombinant MPN141 and/or MPN142 were introduced into mutant IV-22 by transposon delivery in several configurations, and the levels of the P1, B, and C proteins were assessed by immunoblotting. MPN142 in mutant IV-22 has a wild-type nucleotide sequence, yet the introduction of recombinant MPN141 alone to mutant IV-22, although it restored P1 levels, failed to restore levels of B or C. In contrast, recombinant MPN141 and MPN142 delivered in cis or in trans were sufficient to restore all three proteins. Taken together, our data indicated that some but not all synthesis of B or C is dependent on coupling to the translation of P1 immediately upstream of MPN142 and demonstrated that proteins B and C are not stable in the absence of P1. The linkage of MPN141 and MPN142 at the levels of transcription, translation, and protein stability, in addition to their previously demonstrated colocalization and the requirement of B and/or C for P1 function, reinforces the conclusion that these proteins constitute a multiprotein complex that functions in receptor binding.
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PMID:Synthesis, stability, and function of cytadhesin P1 and accessory protein B/C complex of Mycoplasma pneumoniae. 1638 47

The P1, P40, and P90 proteins of Mycoplasma pneumoniae and the MgPa and P110 proteins of Mycoplasma genitalium are immunogenic adhesion proteins that display sequence variation. Consequently, these proteins are thought to play eminent roles in immune evasive strategies. For each of the five proteins, a similar underlying molecular mechanism for sequence variation was hypothesized, i.e., modification of the DNA sequences of their respective genes. This modification is thought to result from homologous recombination of parts of these genes with repeat elements (RepMp and MgPar elements in M. pneumoniae and M. genitalium, respectively) that are dispersed throughout the bacterial genome. Proteins that are potentially involved in homologous DNA recombination have been suggested to be implicated in recombination between these repeat elements and thereby in antigenic variation. To investigate this notion, we set out to study the function of the RecA homologs that are encoded by the M. pneumoniae MPN490 and M. genitalium MG339 genes. Both proteins, which are 79% identical on the amino acid level, were found to promote recombination between homologous DNA substrates in an ATP-dependent fashion. The recombinational activities of both proteins were Mg2+ and pH dependent and were strongly supported by the presence of single-stranded DNA binding protein, either from M. pneumoniae or from Escherichia coli. We conclude that the MPN490- and MG339-encoded proteins are RecA homologs that have the capacity to recombine homologous DNA substrates. Thus, they may play a central role in recombination between repetitive elements in both M. pneumoniae and M. genitalium.
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PMID:The Mycoplasma pneumoniae MPN490 and Mycoplasma genitalium MG339 genes encode reca homologs that promote homologous DNA strand exchange. 1973 94


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