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A 135-kilodalton surface antigen of Mycoplasma hominis PG21 contains multiple directly repeated sequences
S A Ladefoged1, S Birkelund, S Hauge
1Department of Medical Microbiology and Immunology, University of Aarhus, Denmark.
Abstract:
A monoclonal antibody was used to characterize a 135-kDa surface-located membrane protein (Lmp1) generally present in Mycoplasma hominis strains. The monoclonal antibody, 552, was applied to identify the corresponding gene in an expression library of M. hominis PG21 DNA. The M. hominis PG21 lmp1 gene was sequenced, and its gene product was characterized with the goal of elucidating the structure and function of Lmp1. A total of 7,196 bp in the lmp1 region was sequenced. An open reading frame of 4,032 bp, encoding a protein of 1,344 amino acids with a calculated molecular weight of 147,000, was identified. Analysis of the deduced amino acid sequence predicted a hydrophilic protein with a basic pI (10.0). The N-terminal 24 amino acids were a typical leader sequence. Downstream from the first 726 nucleotides, six similar direct repeats of 471 nucleotides were found. In repeat 7, a single-base substitution, C-->A, gave rise to the stop codon of lmp1. Thus, the C-terminal 945 amino acids were encoded by the 471-bp direct repeats. As evidenced by Southern blot analysis, the gene encoding the 135-kDa antigen is part of a multigene family. One of the genes, lmp2, was situated directly downstream from lmp1 where the direct repeats continued.
Insights
Researchers characterized the Mycoplasma hominis surface protein Lmp1 using a monoclonal antibody. Sequencing revealed the lmp1 gene structure, including direct repeats and its multigene family, providing insights into Lmp1
Area of Science:
- Microbiology
- Molecular Biology
- Protein Chemistry
Background:
- Mycoplasma hominis possesses a surface-located membrane protein, Lmp1, found in most strains.
- Characterization of Lmp1 is crucial for understanding its role in M. hominis.
Purpose of the Study:
- To characterize the 135-kDa surface protein Lmp1 from Mycoplasma hominis.
- To identify and sequence the gene encoding Lmp1.
- To elucidate the structure and function of Lmp1.
Main Methods:
- Monoclonal antibody-based identification of the lmp1 gene in an M. hominis PG21 expression library.
- DNA sequencing of the lmp1 gene region (7,196 bp).
- Bioinformatic analysis of the deduced amino acid sequence and Southern blot analysis.
Main Results:
- Identified an open reading frame of 4,032 bp encoding a 1,344-amino acid protein (147 kDa).
- The Lmp1 protein is predicted to be hydrophilic with a basic pI (10.0) and contains a leader sequence.
- Discovered six direct repeats within the gene, with a mutation causing the lmp1 stop codon; the gene belongs to a multigene family (e.g., lmp2).
Conclusions:
- The lmp1 gene structure features direct repeats contributing to the C-terminal protein sequence.
- Lmp1 is part of a multigene family in Mycoplasma hominis.
- Further research can explore the function of Lmp1 and related proteins.