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Methylase activities from Haemophilus influenzae that protect Haemophilus parainfluenzae transforming
Abstract:
Specific methylases that have the properties of deoxyribonucleic acid (DNA) modification enzymes have been isolated from Haemophilus influenzae strain Rd. Two activities ((Methylase IIa and methylase III) were found to protect transforming DNA of H. parainfluenzae from the action of H. influenzae restriction enzymes. To determine the specificty of the protection, a procedure based on biological activity was developed for the separation and purification of the restriction endonucleases from H. influenzae strain Rd. Two endonuclease R activities presumably corresponding to Hind II and Hind III (P. H. Roy and H. O. Smith, 1973; H. O. Smith and K. W. Wilcox, 1970) were characterized by differences in their chromatographic properties, ability to attack T7 DNA, and inactivation of the transforming activity of different markers of H. parainfluenzae DNA. One endonuclease R enzyme (Hind II) attacked T7 DNA and was found to inactivate the dalacin resistance marker (smaller than 0.01% activity remaining) with only a slight effect on the streptomycin resistance marker (83% activity remaining). Methylase IIa treatment protected 40% of the dalacin resistance marker of H. parainfluenzae DNA from inactivation by Hind II. The other restriction activity (Hind III) was inert towards T7 DNA and inactivated the streptomycin resistance marker of H. parainfluenzae DNA (smaller than 0.01% activity remaining) without any effect on the dalacin resistance marker. The methylation of H. parainfluenzae DNA accomplished by methylase III protected 60% of the transforming activity of the streptomycin resistance marker of H. parainfluenzae DNA from the action of Hind III.
Insights
Specific methylases from Haemophilus influenzae protect bacterial DNA from restriction enzymes. Methylase IIa protects against Hind II, while methylase III protects against Hind III, preserving genetic markers.
Area of Science:
- Molecular Biology
- Enzymology
- Bacteriology
Background:
- Deoxyribonucleic acid (DNA) modification enzymes, specifically methylases, are crucial for cellular processes.
- Haemophilus influenzae possesses distinct methylases and restriction enzymes that interact with DNA.
- Understanding these interactions is key to deciphering DNA protection mechanisms.
Purpose of the Study:
- To isolate and characterize specific methylases from Haemophilus influenzae strain Rd.
- To investigate the protective role of these methylases against Haemophilus influenzae restriction enzymes.
- To determine the specificity of methylase protection for different DNA markers.
Main Methods:
- Isolation and purification of specific methylases (Methylase IIa and Methylase III) from H. influenzae.
- Development of a biological activity-based procedure for separating H. influenzae restriction endonucleases (Hind II and Hind III).
- Assessing the protective effect of methylation on transforming DNA markers against restriction enzyme activity.
Main Results:
- Methylase IIa protected the dalacin resistance marker of H. parainfluenzae DNA from Hind II inactivation (40% protection).
- Methylase III protected the streptomycin resistance marker of H. parainfluenzae DNA from Hind III inactivation (60% protection).
- Hind II and Hind III exhibited distinct specificities in DNA cleavage and marker inactivation.
Conclusions:
- Specific methylases from H. influenzae confer protection against cognate restriction enzymes.
- Methylase IIa and Methylase III demonstrate specificities in protecting different DNA markers.
- These findings elucidate the enzymatic basis of DNA modification and restriction in bacteria.