Gene II of phage f1: its functions and its products.

Abstract
Plasmids harboring the amino-terminal part of bacteriophage f1 gene II confer to bacterial [Escherichia coli] cells partial resistance to infection with the male-specific bacteriophages f1 and f2. This effect (IP-2 phenotype) is due to the production of large amounts of a .apprx. 20,000-dalton polypeptide corresponding to the amino-terminal part of gene II protein. Clones producing functional gene II protein in large amounts were isolated. An in vitro assay was developed to test the enzymatic activity of the gene II protein.