Antigenic determinants of the chlamydial major outer membrane protein resolved at a single amino acid level.

ABSTRACT The major outer membrane protein (MOMP), a putative porin and a multifunction surface protein of Campylobacter jejuni, may play an important role in the adaptation of the organism to various host environments. To begin to dissect the biological functions and antigenic features of this protein, the gene (designatedcmp) encoding MOMP was identified and characterized from 22 strains of C. jejuni and one strain of C. coli. It was shown that the single-copy cmp locus encoded a protein with characteristics of bacterial outer membrane proteins. Prediction from deduced amino acid sequences suggested that each MOMP subunit consisted of 18 β-strands connected by short periplasmic turns and long irregular external loops. Alignment of the amino acid sequences of MOMP from different strains indicated that there were seven localized variable regions dispersed among highly conserved sequences. The variable regions were located in the putative external loop structures, while the predicted β-strands were formed by conserved sequences. The sequence homology of cmp appeared to reflect the phylogenetic proximity of C. jejuni strains, since strains with identical cmp sequences had indistinguishable or closely related macrorestriction fragment patterns. Using recombinant MOMP and antibodies recognizing linear or conformational epitopes of the protein, it was demonstrated that the surface-exposed epitopes of MOMP were predominantly conformational in nature. These findings are instrumental in the design of MOMP-based diagnostic tools and vaccines.

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High-resolution mapping of serovar-specific and common antigenic determinants of the major outer membrane protein of Chlamydia trachomatis.

Journal of Experimental Medicine ◽

10.1084/jem.167.3.817 ◽

1988 ◽

Vol 167 (3) ◽

pp. 817-831 ◽

Cited By ~ 78

Author(s):

R S Stephens ◽

E A Wagar ◽

G K Schoolnik

Keyword(s):

Amino Acid ◽

Chlamydia Trachomatis ◽

Membrane Protein ◽

Outer Membrane ◽

Outer Membrane Protein ◽

Antigenic Determinants ◽

Amino Acid Peptide ◽

Antigenic Domains ◽

Species Specific ◽

Specific Determinant

The principal surface protein antigen of Chlamydia trachomatis is the major outer membrane protein (MOMP). The MOMP is antigenically complex. Among the 15 serovars of C. trachomatis, mAbs define serovar-, subspecies-, and species-specific determinants on MOMP. The molecular basis of the antigenic diversity of these proteins is reflected in amino acid variable sequence domains. We have mapped the dominant topographic antigenic determinants of MOMP that are defined by mAbs. Using recombinant DNA approaches we have identified the linear distribution of two antigenic domains. One domain contains a serovar-specific determinant and the other contains subspecies- and species-specific determinants. These antigenic domains correspond to two amino acid sequence variable domains. Synthetic peptides were immunogenic and these resolved the serovar-specific determinant within a 14-amino acid peptide. The subspecies- and species-specific determinants were overlapping within a 16-amino acid peptide.

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Chlamydia pneumoniae Major Outer Membrane Protein Is a Surface-Exposed Antigen That Elicits Antibodies Primarily Directed against Conformation-Dependent Determinants

Infection and Immunity ◽

10.1128/iai.69.5.3082-3091.2001 ◽

2001 ◽

Vol 69 (5) ◽

pp. 3082-3091 ◽

Cited By ~ 45

Author(s):

Katerina Wolf ◽

Elizabeth Fischer ◽

David Mead ◽

Guangming Zhong ◽

Roseanna Peeling ◽

...

Keyword(s):

Monoclonal Antibody ◽

Membrane Protein ◽

Outer Membrane ◽

Outer Membrane Protein ◽

Chlamydia Pneumoniae ◽

Major Outer Membrane Protein ◽

Mass Spectrometry Analysis ◽

Antigenic Determinants ◽

Specific Monoclonal Antibody ◽

Species Specific

ABSTRACT The major outer membrane protein (MOMP) of Chlamydia trachomatis serovariants is known to be an immunodominant surface antigen. Moreover, it is known that the C. trachomatis MOMP elicits antibodies that recognize both linear and conformational antigenic determinants. In contrast, it has been reported that the MOMP of Chlamydia pneumoniae is not surface exposed and is immunorecessive. We hypothesized that the discrepancies betweenC. trachomatis and C. pneumoniae MOMP exposure on intact chlamydiae and immunogenic properties might be because the focus of the host's immune response is directed to conformational epitopes of the C. pneumoniae MOMP. We therefore conducted studies aimed at defining the surface exposure of MOMP and the conformational dominance of MOMP antibodies. We present here a description of C. pneumoniaespecies-specific monoclonal antibody (MAb), GZD1E8, which recognizes a conformational epitope on the surface of C. pneumoniae. This MAb is potent in the neutralization ofC. pneumoniae infectivity in vitro. Another previously described C. pneumoniaespecies-specific monoclonal antibody, RR-402, displayed very similar characteristics. However, the antigenic determinant recognized by RR-402 has yet to be identified. We show by immunoprecipitation ofC. pneumoniae with GZD1E8 and RR-402 MAbs and by mass spectrometry analysis of immunoprecipitated proteins that both antibodies GZD1E8 and RR-402 recognize the MOMP of C. pneumoniae and that this protein is localized on the surface of the organism. We also show that human sera fromC. pneumoniae-positive donors consistently recognize the MOMP by immunoprecipitation, indicating that the MOMP ofC. pneumoniae is an immunogenic protein. These findings have potential implications for both C. pneumoniae vaccine and diagnostic assay development.

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Molecular Cloning, Sequencing, and Expression ofomp-40, the Gene Coding for the Major Outer Membrane Protein from the Acidophilic Bacterium Thiobacillus ferrooxidans

Applied and Environmental Microbiology ◽

10.1128/aem.66.6.2318-2324.2000 ◽

2000 ◽

Vol 66 (6) ◽

pp. 2318-2324 ◽

Cited By ~ 37

Author(s):

Nicolas Guiliani ◽

Carlos A. Jerez

Keyword(s):

Amino Acid ◽

Membrane Protein ◽

Amino Acid Sequence ◽

Outer Membrane ◽

Outer Membrane Protein ◽

Thiobacillus Ferrooxidans ◽

Sodium Dodecyl ◽

Major Outer Membrane Protein ◽

Gene Coding ◽

Chemolithoautotrophic Bacteria

ABSTRACT Thiobacillus ferrooxidans is one of the chemolithoautotrophic bacteria important in industrial biomining operations. Some of the surface components of this microorganism are probably involved in adaptation to their acidic environment and in bacterium-mineral interactions. We have isolated and characterizedomp40, the gene coding for the major outer membrane protein from T. ferrooxidans. The deduced amino acid sequence of the Omp40 protein has 382 amino acids and a calculated molecular weight of 40,095.7. Omp40 forms an oligomeric structure of about 120 kDa that dissociates into the monomer (40 kDa) by heating in the presence of sodium dodecyl sulfate. The degree of identity of Omp40 amino acid sequence to porins from enterobacteria was only 22%. Nevertheless, multiple alignments of this sequence with those from several OmpC porins showed several important features conserved in the T. ferrooxidans surface protein, such as the approximate locations of 16 transmembrane beta strands, eight loops, including a large external L3 loop, and eight turns which allowed us to propose a putative 16-stranded beta-barrel porin structure for the protein. These results together with the previously known capacity of Omp40 to form ion channels in planar lipid bilayers strongly support its role as a porin in this chemolithoautotrophic acidophilic microorganism. Some characteristics of the Omp40 protein, such as the presence of a putative L3 loop with an estimated isoelectric point of 7.21 allow us to speculate that this can be the result of an adaptation of the acidophilic T. ferrooxidans to prevent free movement of protons across its outer membrane.

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