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Characterization of a 3.5-kbp plasmid from Helicobacter pylori
J A Minnis1, T E Taylor, J E Knesek
1Biology Department, Texas Woman's University, Denton 76204, USA.
Abstract:
A 3.5-kbp plasmid (pHPM180) was isolated from Helicobacter pylori (HPM180) and the DNA sequence was determined. Two open reading frames (ORF1 and ORF2) were identified which could encode polypeptides of 54,517 and 27,629 Da, respectively. Ribosome binding and promoter consensus sequences were identified, as well as two 232-bp direct repeats and four 22-bp direct repeats. DNA sequence homology was found between pHPM180 ORF1 and a 684-base pair HindIII fragment from a 5.6-kbp H. pylori plasmid. ORF1 showed amino acid homology with six replication proteins from bacterial plasmids with theta-type replicons. Additional sequence identity was found between pHPM180 noncoding DNA and a segment of H. pylori pHPK255, a plasmid that replicates via a rolling circle type mechanism. A ribonuclease protection assay determined that ORF1 was transcribed in H. pylori HPM180.
Insights
Researchers sequenced the Helicobacter pylori plasmid pHPM180, identifying two open reading frames (ORFs) and repeat sequences. The study found homology to bacterial replication proteins, suggesting plasmid replication functions.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- Helicobacter pylori is a significant human pathogen.
- Plasmids play crucial roles in bacterial adaptation and virulence.
- Understanding plasmid biology in H. pylori is essential for developing novel therapeutic strategies.
Purpose of the Study:
- To characterize the genetic elements of the novel Helicobacter pylori plasmid pHPM180.
- To identify potential functional genes and regulatory sequences within the plasmid.
- To investigate the evolutionary relationships of pHPM180 with other known plasmids.
Main Methods:
- Plasmid DNA isolation and purification.
- Comprehensive DNA sequencing and sequence analysis.
- Bioinformatic analysis for open reading frame (ORF) identification and homology searches.
- Ribonuclease protection assay for gene transcription analysis.
Main Results:
- The 3.5-kbp plasmid pHPM180 was fully sequenced.
- Two ORFs (ORF1 and ORF2) encoding polypeptides of 54,517 and 27,629 Da were identified.
- Homology was observed between ORF1 and bacterial theta-type replication proteins, and between noncoding DNA and a rolling circle replicating plasmid.
- Direct repeat sequences (232-bp and 22-bp) and consensus promoter sequences were identified.
- ORF1 was confirmed to be transcribed in H. pylori HPM180.
Conclusions:
- The genetic and sequence analysis of pHPM180 provides insights into its replication and maintenance mechanisms.
- The identified ORFs and regulatory elements suggest functional roles for this plasmid in H. pylori.
- Comparative sequence analysis indicates potential horizontal gene transfer events and evolutionary links to other bacterial plasmids.