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Cloning and characterization of a Prevotella melaninogenica hemolysin
1Department of Oral Biology, University of Florida College of Dentistry, Gainesville 32610, USA.
Abstract:
Hemolysins have been proven to be important virulence factors in many medically relevant pathogenic organisms. Their production has also been implicated in the etiology of periodontal disease. Hemolytic strain 361B of Prevotella melaninogenica, a putative etiologic agent of periodontal disease, was used in this study. The cloning, sequencing, and characterization of phyA, the structural gene for a P. melaninogenica hemolysin, is described. No extensive sequence homology could be identified between phyA and any reported sequence at either the nucleotide or amino acid level. As predicted from sequence analysis, this gene produces a 39-kDa protein which has hemolytic activity as measured by zymogram analysis. Unlike many Ca2+-dependent bacterial hemolysins, both the cloned and native PhyA proteins were enhanced by the presence of EDTA in a dose-dependent fashion with 40 mM EDTA allowing maximum activity. Ca2+ and Mg2+ were found to be inhibitory. The hemolytic activity also was found to have a dose-dependent endpoint. Through recovery of hemolytic activity from a spent reaction, this endpoint was shown to be the result of end product inhibition. This is the first report describing the cloning and sequencing of a gene from P. melaninogenica.
Insights
Researchers cloned and sequenced phyA, the gene for a Prevotella melaninogenica hemolysin. This novel hemolysin is enhanced by EDTA and inhibited by calcium, offering new insights into periodontal disease pathogenesis.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- Hemolysins are key virulence factors in pathogenic organisms.
- Hemolysin production is linked to the development of periodontal disease.
- Prevotella melaninogenica is a suspected cause of periodontal disease.
Purpose of the Study:
- To clone, sequence, and characterize the hemolysin gene (phyA) from a hemolytic strain of Prevotella melaninogenica.
- To investigate the biochemical properties of the encoded hemolysin protein.
- To establish a genetic basis for hemolysin production in P. melaninogenica.
Main Methods:
- Cloning and sequencing of the phyA gene.
- Expression and purification of the PhyA protein.
- Zymogram analysis to assess hemolytic activity.
- Enzyme kinetics studies to determine optimal activity conditions and inhibition.
Main Results:
- The phyA gene was successfully cloned and sequenced, revealing no significant homology to known sequences.
- The gene encodes a 39-kDa protein (PhyA) with demonstrated hemolytic activity.
- PhyA activity is enhanced by EDTA and inhibited by Ca2+ and Mg2+, differing from typical Ca2+-dependent hemolysins.
- Hemolytic activity exhibits a dose-dependent endpoint due to end-product inhibition.
Conclusions:
- This study reports the first cloning and sequencing of a gene from Prevotella melaninogenica.
- The characterized hemolysin (PhyA) possesses unique biochemical properties, including EDTA enhancement and cation inhibition.
- Understanding PhyA's function provides novel insights into the virulence mechanisms of P. melaninogenica in periodontal disease.
