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PubMed2004

Crystallization and preliminary crystallographic studies of MOMP (major outer membrane protein) from Campylobacter jejuni.

Campylobacter jejuni is the leading bacterial cause of human enteritis linked to ingestion of contaminated food or water. MOMP, the major outer membrane protein from these Gram-negative bacteria, belongs to the porin family. In order to determine the three-dimensional structure of this protein and to elucidate the underlying molecular mechanisms, the MOMP from C. jejuni strain 85H has been purified and crystallized by vapour diffusion. Two crystal forms were characterized for this membrane protein. X-ray diffraction data were collected to a resolution of 3.1 A using a synchrotron-radiation source from the orthorhombic crystal form, which belonged to space group P2(1)2(1)2 with unit-cell parameters a = 170.1, b = 101.9, c = 104.9 A. With a trimer in the asymmetric unit, the solvent content is 64% (V(M) = 3.4 A Da(-1)). The other form exhibits trigonal symmetry (space group R3) with hexagonal unit-cell parameters a = b = 94.2, c = 161.2 A, but diffracts X-rays poorly to about 4 A with significant anisotropy.

Bacterial Proteins↗
PubMed2000

MOMP (major outer membrane protein) of Campylobacter jejuni; a versatile pore-forming protein.

The great majority of trimeric porins of Gram-negative bacteria cannot be dissociated into monomers without disrupting their folded conformation. The porin of Campylobacter jejuni, however, displays two folded structures, a classical oligomer and a monomer resistant to detergent denaturation. We probed the transition of trimer to monomer using light scattering experiments and examined the secondary structures of these two molecular states by infra-red spectroscopy. The channel-forming properties of both trimer and monomer were studied after incorporation into artificial lipid bilayers. In these conditions, the trimer induced ion channels with a conductance value of 1200 pS in 1 M NaCl. The pores showed marked cationic selectivity and sensitivity to low voltage. Analysis of the isolated monomer showed nearly the same single-channel conductance and the same selectivity and sensitivity to voltage. These results indicate that the folded monomer form of C. jejuni MOMP displays essentially the same pore-forming properties as the native trimer.

Antigens, Bacterial↗
PubMed2000

Immunity to Chlamydia pneumoniae induced by vaccination with DNA vectors expressing a cytoplasmic protein (Hsp60) or outer membrane proteins (MOMP and Omp2).

Immune responses induced by intramuscular DNA immunization with Chlamydia pneumoniae genes coding for the major outer membrane protein (MOMP), cysteine-rich outer membrane protein 2 (Omp2) or the heat shock protein 60 (Hsp60) were studied. BALB/c mice were vaccinated intramuscularly three times at 3-week intervals and challenged intranasally 2 weeks after the last injection. Immunization with pmomp or phsp60 showed 1.2-1.5 log reduction in the mean lung bacterial counts after the challenge. Specific antibodies were detected only in sera of the mice immunized with pomp2 and phsp60. Although immunization with pomp2 resulted in a strong serum antibody response against Omp2 protein, it failed to protect the mice. Immunization with any of the three vaccines did not reduce the severity of histologically assessed pneumonia, but resulted in significantly higher lymphoid reaction in the lung indicating immunological memory.

Animals↗
PubMed2002

Immunoblotting analysis of abdominal aortic aneurysms using antibodies against Chlamydia pneumoniae recombinant MOMP.

OBJECTIVES: antibodies against Chlamydia pneumoniae have been associated with atherosclerosis and with expansion of abdominal aortic aneurysms (AAA). C. pneumoniae has been demonstrated in coronary arteries, AAA and the carotid arteries by use of polymerase chain reactions (PCR), immunohistochemical procedures and electron microscopy. However, the correlation between demonstrating C. pneumoniae DNA or antigen in tissue from plaque material or aneurysms and the antibody titres in serum is controversial. The specificity of immunohistochemical procedures is unknown. The aim of this study was to assess the possibility of potential non-specific findings for methods based on immunostaining. MATERIALS AND METHODS: twenty patients undergoing infrarenal AAA repair were studied. Full AAA thickness tissue was collected from the anterior wall of the aneurysm. Analysis was performed using polyacrylamide gelelectrophoresis, immunoblotting and mass spectrometric protein identification. RESULTS: C. pneumoniae antigen was not demonstrated in any of the AAA samples, whereas a major cross-reacting protein was present in all AAA samples. The protein was identified as the human haemoglobin beta chain. CONCLUSION: we were not able to find C. pneumoniae antigens reacting with an anti C. pneumoniae major outer membrane protein (MOMP). Direct detection of C. pneumoniae by immunohistostaining procedures should be interpreted with caution due to potential crossreaction with non chlamydial proteins.

Aged↗
PubMed2006

An increase in MPC-1- and MPC-1-CD45+ immature myeloma cells in the progressive states of bone marrow plasmacytosis: the revised phenotypic classification of monoclonal marrow plasmacytosis (MOMP-2005).

The heterogeneity of bone marrow plasmacytosis is clearly analyzed by multicolor staining with anti-CD38 antibody. To date, at least 5 subpopulations of plasma cells have been identified in the bone marrow of multiple myeloma (MM) patients with regard to the expression of MPC-1, CD49e (VLA-5), and CD45: MPC-1(-)CD49e(-)CD45(+) proliferative immature cells, MPC-1(-)CD49e(-)CD45(-) immature myeloma cells, MPC-1(+)CD49e(-)CD45(-) and MPC-1(+)CD49e(-)CD45(+) intermediate myeloma cells, and MPC-1(+)CD49e(+)CD45(+) mature myeloma cells. We performed phenotypic analyses in 75 cases of monoclonal bone marrow plasmacytosis, including 46 cases of MM and 29 cases of monoclonal gammopathy of undetermined significance (MGUS). In 31 cases of progressive MM disease, MPC-1(-) immature and MPC-1(-)CD45(+) proliferative immature myeloma cells were significantly increased up to >25% and >10%, respectively, of the plasma cell fractions (CD38(++) cells), whereas there were no increases in MPC-1(-) or MPC-1(-)CD45(+) proliferative immature myeloma cells in 15 cases of stable disease. Interestingly, the proportions of MPC-1(-) and MPC-1(-)CD45(+) immature monoclonal plasma cells also increased in the 7 progressive cases of MGUS. Finally, we present the revised (2005) phenotypic classification of monoclonal marrow plasmacytosis (MOMP-2005).

Antigens, CD↗
PubMed1999

Effect of normal and immune sera on Haemophilus ducreyi 35000HP and its isogenic MOMP and LOS mutants.

A bactericidal assay was developed in order to test the effect of hyperimmune rabbit sera on the viability of serum-resistant Haemophilus ducreyi 35000HP. Testing of several lots of rabbit complement and time course experiments showed that the serum-sensitive H. ducreyi CIPA77 was killed efficiently by 25% complement at 35 degrees C in 3 h. We hypothesized that incubation of 35000HP under these conditions with the appropriate bactericidal antibody would kill this strain. A panel of high titre rabbit antisera was developed and tested against 35000HP. The panel included antisera raised to whole cells, total membranes, Sarkosyl-insoluble outer membrane proteins, the H. ducreyi lipoprotein, and the peptidoglycan-associated lipoprotein. None of the antisera convincingly showed bactericidal activity. The bactericidal assay was also used to determine the effect of normal human serum (NHS) on isogenic mutants of 35000HP. 35000HP-RSM2, an Omegakan insertion mutant that expresses a truncated lipooligosaccharide, was as resistant to NHS as its parent. A mutant deficient in expression of the major outer membrane protein (35000. 60) was sensitive to NHS. We conclude that 35000HP is relatively resistant to normal and hyperimmune sera, and that the major outer membrane protein contributes to this resistance.

Animals↗
PubMed1995

Protective efficacy of a parenterally administered MOMP-derived synthetic oligopeptide vaccine in a murine model of Chlamydia trachomatis genital tract infection: serum neutralizing IgG antibodies do not protect against chlamydial genital tract infection.

The protective efficacy of an alum-adsorbed, parenterally administered synthetic oligopeptide immunogen corresponding to antigenically common T-helper and neutralizing B-cell epitopes of the Chlamydia trachomatis major outer membrane protein was studied in a murine model of chlamydial genital tract infection. Mice produced high levels of anti-chlamydial serum IgG neutralizing antibodies following subcutaneous immunization with the alum-adsorbed oligopeptide. Lower but detectable levels of chlamydial specific IgG antibodies were found in vaginal washes. IgG1 was the predominant isotype present in sera and vaginal washes. Chlamydial-specific IgA was not present in either the sera or vaginal washes of immunized mice. Vaccinated and control mice were challenged intravaginally or intrauterinally with low, medium, or high doses of C. trachomatis serovar D challenge inocula. Protection was assessed by performing quantitative chlamydial cervico-vaginal cultures over the course of the infection period. There were no statistically significant differences between groups of immunized and control mice in either colonization, shedding, or duration of infection. These findings demonstrate that parenteral immunization with the oligopeptide (serum-neutralizing antibodies) is ineffective in preventing chlamydial genital tract infection. It is possible, since chlamydial infection is restricted to the genital tract mucosae, that a more accurate evaluation of the oligopeptide vaccine potential will require local rather than systemic immunization.

Administration, Intravaginal↗
PubMed2004

Recombinant major outer membrane protein (MOMP) of Chlamydophila abortus, Chlamydophila pecorum, and Chlamydia suis as antigens to distinguish chlamydial species-specific antibodies in animal sera.

Recombinant major outer membrane proteins (rMOMP) of Chlamydophila (Ch.) abortus, Ch. pecorum, and Chlamydia (C.) suis were used as antigens to distinguish chlamydial species-specific antibodies in (i) immune sera from six rabbits and three pigs raised against native purified elementary bodies, (ii) serum samples from 25 sows vaccinated with Ch. abortus, and (iii) 40 serum samples from four heifers experimentally infected with Ch. abortus. All post-exposition sera contained chlamydial antibodies as confirmed by strong ELISA seroreactivities against the chlamydial LPS. For the rMOMP ELISA mean IgG antibody levels were at least 5.8-fold higher with the particular rMOMP homologous to the chlamydial species used for immunisation or infection than with heterologous rMOMPs (P <0.001). Preferential rMOMP ELISA reactivities of sera were confirmed by Western blotting. The results suggest that the entire chlamydial rMOMP could provide a species-specific serodiagnostic antigen.

Animals↗
PubMed1994

Purification, pore-forming ability, and antigenic relatedness of the major outer membrane protein of Shigella dysenteriae type 1.

The major outer membrane protein (MOMP), the most abundant outer membrane protein, was purified to homogeneity from Shigella dysenteriae type 1. The purification method involved selective extraction of MOMP with sodium dodecyl sulfate in the presence of 0.4 M sodium chloride followed by size exclusion chromatography with Sephacryl S-200 HR. MOMP was found to form hydrophilic diffusion pores by incorporation into artificial liposome vesicles composed of egg yolk phosphatidylcholine and dicetylphosphate, indicating that MOMP of S. dysenteriae type 1 exhibited significant porin activity. However, the liposomes containing heat-denatured MOMP were barely active. The molecular weight of MOMP found by size exclusion chromatography was 130,000, and in sodium dodecyl sulfate-10% polyacrylamide gel it moved as an oligomer of 78,000 molecular weight. Upon boiling, fully dissociated monomers of 38,000 molecular weight were seen for S. dysenteriae type 1. However, among the four Shigella spp., the monomeric MOMP generated upon boiling ranged from 38,000 to 35,000 in molecular weight. Antibody raised in BALB/c mice immunized with MOMP of S. dysenteriae type 1 reacted strongly with purified MOMP of S. dysenteriae type 1 in an enzyme-linked immunosorbent assay (ELISA). The antibody reacted with whole-cell preparations of S. dysenteriae type 1 in an ELISA, suggesting that MOMP possessed surface components. Moreover, MOMP could be visualized on the bacterial surface by immunoelectron microscopy with anti-MOMP antibody. S. dysenteriae type 1 MOMP-specific immunoglobulin eluted from MOMP bound to a nitrocellulose membrane was found to cross-react with MOMP preparations of S. flexneri, S. boydii, and S. sonnei, indicating that MOMPs were antigenically related among Shigella species. The strong immunogenicity, surface exposure, and antigenic relatedness make MOMP of Shigella species an immunologically significant macromolecule for study.

Animals↗
PubMed1990

Antibody response to epitopes of chlamydial major outer membrane proteins on infectious elementary bodies and of the reduced polyacrylamide gel electrophoresis-separated form.

Approximately 60% of the outer membrane of chlamydial elementary bodies (EBs) consists of the major outer membrane protein (MOMP) that has structural and metabolic functions. The antigenic properties of MOMPs from mammalian strains of serovars 1 and 2 and an avian strain of Chlamydia psittaci were analyzed. Polyclonal-monospecific antisera (PMAs), one monoclonal antibody (MAb), and polyclonal antisera (PAs) were produced against reduced polyacrylamide gel electrophoresis-separated MOMPs and against infectious EBs. Three PMAs and the MAb, which were induced by reduced polyacrylamide gel electrophoresis-separated MOMPs, reacted strongly in Western blot (immunoblot) assays with MOMPs of serovar 1 and 2 strains as well as with that of the avian strain 6BC, and two of these PMAs reacted weakly (dilution, 1:20) with the MOMP of strain LGV-2. The third PMA and the MAb against the MOMP of the serovar 2 strain did not react with the MOMP of LGV-2. Four PAs were produced against infectious EBs of the serovar 1 strain. One of these PAs reacted with the homologous MOMP and that of the avian strain 6BC but did not recognize MOMPs of other chlamydial strains. Three of the PAs reacted with MOMPs of homologous strains only and failed to recognize MOMPs of avian, serovar 2, and LGV-2 strains. Five PAs induced against infectious EBs of the serovar strain 2 reacted only with the MOMPs of the homologous strains and failed to recognize MOMPs of other strains of chlamydiae. Consequently, MOMPs of C. psittaci strains possess genus-, species-, and serovar-specific epitopes whereby the immune response to serovar-specific epitopes of MOMP predominate when infectious EBs are used for immunization.

Animals↗
PubMed1995

A new phenotypic classification of bone marrow plasmacytosis.

Here, we propose a new phenotypic classification of bone marrow plasmacytosis. By 2-color phenotypic analysis with FITC anti-CD38 and PE anti-CD19, -CD56, -VLA-5 or MPC-1 antibody, plasma cells are easily identified on the histogram, even though no more than 1% of plasma cells are found in the bone marrow. Hence, plasma cells are phenotypically classified into polyclonal (reactive) (CD19+CD56-) or monoclonal (neoplastic) plasma cells (mostly CD19-CD56+), and furthermore immature (VLA-5-MPC-1-), intermediate (VLA-5-MPC-1+) and mature plasma cells (VLA-5+MPC-1+). According to these findings, plasmacytosis in the bone marrow can be classified into polyclonal marrow plasmacytosis (POMP) and monoclonal marrow plasmacytosis (MOMP) states. The MOMP state is further subclassified into MOMP-1 and MOMP-2, MOMP-3 and MOMP-4; MOMP-1 is defined by co-existence of monoclonal plasma cells and polyclonal plasma cells, and MOMP-2 to MOMP-4 are dependent on increased proportions of VLA-5-MPC-1- immature myeloma (plasma) cells. We found that the cases of benign monoclonal gammopathy (BMG) according to the conventional classification were in the MOMP-1 state, and myelomas could be classified into the MOMP-2 to MOMP-4 state. Subclassification of the MOMP state may be useful in determining the prognosis of myelomas, where an increase in immature myeloma cells is reported to correlate well with their aggravation during the clinical courses. Therefore, this new phenotypic classification of bone marrow plasmacytosis (POMP and MOMP-1 to MOMP-4) will contribute to differential diagnosis and understanding of therapeutic responses and prognosis in myelomas.

Antigens, CD19↗
PubMed2005

Molecular characterization of the major outer membrane protein of Haemophilus somnus.

The major outer membrane protein (MOMP) of Haemophilus somnus shows antigenic and molecular mass diversity that forms the basis of a preliminary grouping system for H. somnus strains. In this study, the gene encoding MOMP of H. somnus strain 8025 was cloned in three overlapping fragments by PCR techniques, and then sequenced. The gene consists of a 1164-bp open reading frame encoding a deduced 380-amino acid protein with a 19-amino acid signal sequence, giving a mature protein with a calculated molecular mass of 39,913 Da. Significant homology was found between MOMP and porin protein sequences of bacteria in Pasteurellaceae species. When expressed in Escherichia coli, the protein from the MOMP gene directed by the T7 promoter was identical in size (approximately 40 kDa) to native MOMP and reacted with MOMP-specific antibodies. Comparisons of the MOMP gene sequences from six unrelated strains of H. somnus to that of strain 8025 revealed that the genes of three MOMP type 1 strains were highly conserved with that of strain 8025 in length and sequence. However, two MOMP type 3c strains and one MOMP type 3a strain differed markedly from the MOMP of strain 8025 in their 3'-terminal halves. Their deduced MOMP amino acid sequences differed in sequence (3c, 80.5 and 82.7% identity; 3a, 62.4% identity) and in length (3c, 384 and 376; 3a, 316), indicating that the molecular differences are the basis of antigenicity and molecular mass differences of H. somnus MOMP. In the predicted MOMP secondary structure, the variable sequences primarily mapped to putative surface-exposed loops, and a variable and surface-exposed epitope of MOMP-specific antibody was identified in the seventh-largest loop. These findings are useful for understanding the structural and immunological characteristics of H. somnus.

Amino Acid Sequence↗
PubMed1993

Expression and translocation of the chlamydial major outer membrane protein in Escherichia coli.

The entire gene encoding the major outer membrane protein (MOMP) from Chlamydia psittaci strain GPIC has been cloned and expressed in Escherichia coli. A tightly regulated T7 promoter is used to control expression of the protein in Escherichia coli. Upon induction of expression, the precursor (pre-MOMP) is synthesized in the cell. This is followed by the appearance of a lower molecular weight protein that comigrates with mature MOMP from chlamydial elementary bodies by both one-dimensional sodium dodecyl sulfate polyacrylamide gel electrophoresis and two-dimensional gel electrophoresis. When E. coli cells expressing MOMP are converted to spheroplasts and subjected to protease treatment, MOMP is quantitatively degraded while cytoplasmic pre-MOMP is protected from degradation. Whole cells subjected to the same protease treatment show no degradation of MOMP. Furthermore, MOMP is not detected in surface-labeling experiments using several MOMP-specific antibodies. These data indicate that pre-MOMP is translocated to the periplasmic space and processed but is not surface exposed in E. coli. Expression of MOMP in this system causes a significant reduction in cell viability. In addition, coexpression in E. coli of MOMP or a MOMP-PhoA fusion with various chaperone proteins does not alter the level of MOMP translocation.

Amino Acid Sequence↗
PubMed1992

Overexpression and surface localization of the Chlamydia trachomatis major outer membrane protein in Escherichia coli.

The Chlamydia trachomatis major outer membrane protein (MOMP) is the quantitatively predominant surface protein which has important functional, structural and antigenic properties. We have cloned and overexpressed the MOMP in Escherichia coli. The MOMP is surface exposed in C. trachomatis and capable of eliciting protective antibodies in infected hosts, and therefore has potential as a candidate vaccine to prevent infection with this significant human pathogen. The recombinant MOMP clone, L2rMOMP, contained the entire MOMP gene including the encoded leader sequence. Large quantities of chlamydial MOMP were expressed, some of which was processed and translocated to the E. coli surface. Surface localization of the MOMP was demonstrated by the binding of anti-MOMP monoclonal antibodies to the surface of the induced clone, and was visualized by fluorescence and electron microscopy. The induction of MOMP expression had a rapidly lethal effect on the L2rMOMP E. coli clone. Although no genetic system exists for Chlamydia, development of a stable, inducible E. coli clone which overexpresses the chlamydial MOMP permits a study of the biological properties of the MOMP, including the contribution of the MOMP variable segments to the topographical interactions which determine the antigenic structure responsible for human immune response.

Antibodies, Bacterial↗
PubMed1985

Purification of Legionella pneumophila major outer membrane protein and demonstration that it is a porin.

We have purified the major outer membrane protein (MOMP) of Legionella pneumophila, determined that it is associated with peptidoglycan, and characterized it as a porin. To purify the MOMP, we used a simple, rapid, three-step procedure that gave us the protein in high yield. The first step of the purification procedure involved selectively extracting the MOMP from whole bacterial cells with calcium and zwitterionic detergent. The second and third steps achieved purification by ion-exchange and molecular-sieve chromatography. The dissociation of the MOMP into monomers was dependent upon the presence of a reducing agent and was enhanced by treatment at 100 degrees C. To study the relationship of the MOMP to peptidoglycan, we extracted the protein by a modification of the Rosenbusch procedure. Like the Escherichia coli porins, the MOMP was peptidoglycan associated. The MOMP was at least partially dissociated from peptidoglycan in sodium dodecyl sulfate and a high salt concentration. To study the ion channel-forming properties of the MOMP, we reconstituted the MOMP in planar lipid membranes. The MOMP formed ion-permeable channels with a single-channel conductance size of 100 picoSiemens. The MOMP channels exhibited a fourfold selectivity for cations over anions and voltage-independent gating. These findings demonstrate that the MOMP is a porin with properties similar to those of E. coli porins.

Bacterial Outer Membrane Proteins↗
PubMed2005

Surface expression, single-channel analysis and membrane topology of recombinant Chlamydia trachomatis Major Outer Membrane Protein.

BACKGROUND: Chlamydial bacteria are obligate intracellular pathogens containing a cysteine-rich porin (Major Outer Membrane Protein, MOMP) with important structural and, in many species, immunity-related roles. MOMP forms extensive disulphide bonds with other chlamydial proteins, and is difficult to purify. Leaderless, recombinant MOMPs expressed in E. coli have yet to be refolded from inclusion bodies, and although leadered MOMP can be expressed in E. coli cells, it often misfolds and aggregates. We aimed to improve the surface expression of correctly folded MOMP to investigate the membrane topology of the protein, and provide a system to display native and modified MOMP epitopes. RESULTS: C. trachomatis MOMP was expressed on the surface of E. coli cells (including "porin knockout" cells) after optimizing leader sequence, temperature and medium composition, and the protein was functionally reconstituted at the single-channel level to confirm it was folded correctly. Recombinant MOMP formed oligomers even in the absence of its 9 cysteine residues, and the unmodified protein also formed inter- and intra-subunit disulphide bonds. Its topology was modeled as a (16-stranded) beta-barrel, and specific structural predictions were tested by removing each of the four putative surface-exposed loops corresponding to highly immunogenic variable sequence (VS) domains, and one or two of the putative transmembrane strands. The deletion of predicted external loops did not prevent folding and incorporation of MOMP into the E. coli outer membrane, in contrast to the removal of predicted transmembrane strands. CONCLUSIONS: C. trachomatis MOMP was functionally expressed on the surface of E. coli cells under newly optimized conditions. Tests of its predicted membrane topology were consistent with beta-barrel oligomers in which major immunogenic regions are displayed on surface-exposed loops. Functional surface expression, coupled with improved understanding of MOMP's topology, could provide modified antigens for immunological studies and vaccination, including live subunit vaccines, and might be useful to co-express MOMP with other chlamydial membrane proteins.

Cell Membrane↗