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The hsd (host specificity) genes of E. coli K 12
Molecular & General Genetics : MGG
|January 1, 1980
Summary
Researchers cloned E. coli K-12 hsd genes using lambda phage, identifying three genes (hsdR, M, S) essential for restriction and modification. Gene order and transcription were determined, revealing distinct promoters and polypeptide products.
Area of Science:
- Molecular Biology
- Genetics
- Microbiology
Background:
- The hsd genes in E. coli K-12 are crucial for host-specific restriction and modification systems.
- Understanding these genes is vital for bacterial genetics and molecular biology research.
Purpose of the Study:
- To clone and characterize the hsd genes of E. coli K-12.
- To determine the genetic organization, transcription, and protein products of the hsdR, hsdM, and hsdS genes.
Main Methods:
- Cloning of hsd genes into lambda phage using in vitro and in vivo techniques.
- Complementation tests to identify functional genes.
- DNA analysis of deletion derivatives to establish gene order.
- SDS-polyacrylamide gel electrophoresis to analyze polypeptide products.
Main Results:
- Identified and cloned three genes: hsdR, hsdM, and hsdS, essential for K-specific restriction and modification.
- Established the gene order as R, M, S and identified two distinct promoters.
- Characterized the molecular weights of the polypeptide products for each gene.
- Demonstrated homology between E. coli K-12 and E. coli B hsd genes, but not with E. coli C.
Conclusions:
- The hsdR, M, and S genes are closely linked and transcribed in the same direction.
- The hsdS gene product shows variation between E. coli strains.
- The cloned genes provide a basis for further studies on restriction-modification mechanisms.