A New Relaxed Mutant of Escherichia coli with an Altered 50S Ribosomal Subunit

A new relaxed mutant called rel C has been isolated from a rel A(+)/rel A(+) partial diploid strain. The rel C mutant is unable to synthesize ppGpp or pppGpp in vivo in response to amino acid starvation or in vitro, but can synthesize these nucleotides in a shift-down. Rel C maps near rif. Studies in vitro demonstrate the lesion to be probably in one of the 50S ribosomal proteins that can be removed by 1.0 M LiCl.