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Sequence analysis and characterization of the hmw gene cluster of Mycoplasma pneumoniae
L B Dirksen1, T Proft, H Hilbert
1Department of Microbiology, University of Georgia, Athens 30602, USA.
Abstract:
Mycoplasma pneumoniae (Mp) cytadherence requires the proper anchoring of cytadhesin proteins in the mycoplasmal membrane at an attachment organelle through their interaction with a cytoskeleton-like network of accessory proteins that includes HMW1 and HMW3. Approximately 8.25 kb of Mp DNA was sequenced, beginning at the 3' end of the hmw3 gene and continuing through hmw1. Comparison of the resulting deduced amino acid (aa) sequence with N terminus and internal peptide aa sequences from purified HMW1 permitted definitive identification of hmw1. HMW1 was characterized with respect to structure, hydrophobicity, possible phosphoacceptor sites and expression of the Mp recombinant protein in Escherichia coli. In addition, HMW1 membrane topography was examined for antibody accessibility on the mycoplasmal surface. hmw3 and hmw1 flank four open reading frames (ORFs) spanning approximately 4.3 kb and in the same orientation as the hmw genes. The sequences of their deduced products were evaluated for likely structural features and comparison with protein data banks. Finally, the Mp rpsD analog was identified immediately downstream from hmw1.
Insights
Mycoplasma pneumoniae cytadherence involves HMW1 and HMW3 proteins. This study sequenced the DNA region containing hmw1 and identified its structure, expression, and surface accessibility, aiding in understanding bacterial attachment.
Area of Science:
- Microbiology
- Molecular Biology
- Genomics
Background:
- Mycoplasma pneumoniae cytadherence relies on cytadhesin proteins anchored by accessory proteins like HMW1 and HMW3.
- These proteins form a cytoskeleton-like network essential for bacterial attachment.
Purpose of the Study:
- To sequence and identify the hmw1 gene and its encoded protein in Mycoplasma pneumoniae.
- To characterize the structure, expression, and surface topography of HMW1.
- To analyze flanking open reading frames and identify other relevant genes.
Main Methods:
- DNA sequencing of approximately 8.25 kb of Mycoplasma pneumoniae DNA.
- Amino acid sequence comparison for definitive gene identification.
- Biochemical characterization of HMW1 (structure, hydrophobicity, phosphoacceptor sites).
- Recombinant protein expression in Escherichia coli.
- Antibody accessibility studies for membrane topography analysis.
Main Results:
- The hmw1 gene was definitively identified and sequenced.
- HMW1 protein characteristics including structure, hydrophobicity, and potential phosphorylation sites were determined.
- HMW1 was expressed recombinantly in E. coli, and its surface accessibility on M. pneumoniae was confirmed.
- Four flanking ORFs and the Mycoplasma pneumoniae rpsD analog were identified downstream of hmw1.
Conclusions:
- The study provides a comprehensive characterization of the HMW1 protein, crucial for Mycoplasma pneumoniae cytadherence.
- The identified flanking ORFs and rpsD analog offer further insights into the genetic organization and functional pathways of M. pneumoniae.
- Understanding these components aids in elucidating the mechanism of bacterial attachment and potential therapeutic targets.