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Title: Type I restriction systems of Escherichia coli
Author: Barcus, Victoria Anne
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1993
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Of the three types of restriction and modification (r-m) systems in Enterobacteriaceae, type I are the most complex both in structure and in function. Three genes, hsdR, M and S encode the multisubunit enzyme. While the products of the hsdM and S genes can form a methylase, the products of all three genes together form an enzyme which functions as both an endonuclease and a methylase. The product of the hsdS gene confers sequence specificity to both the restriction and modification activities. Eleven known type I r-m systems have been separated into three families on the basis of complementation tests, immunological cross-reactivity, and DNA hybridization of their coding sequences. The genes for two of the families reside at the same location on the chromosome, those of the third may be plasmid-encoded. Each member of a family recognizes a unique DNA sequence. Sequence homologies within families allow the use of probes for detection of related genes in other bacteria. While research on type I systems has focused on their mechanism of action and their genetic determinants, extensive surveys for their presence among E.coli strains have not been documented. An understanding of the prevalence and diversity of type I r-m systems in natural populations is basic to any consideration of either their relevance to a bacterial population or of the evolutionary forces acting at the hsd locus. This thesis describes the use of biological and molecular screens to determine the distribution and diversity of type I r-m systems in natural isolates of E.coli.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available