Characterization of a gene, glnL, the product of which is involved in the regulation of nitrogen utilization in Escherichia coli

DNA was prepared from a strain of Escherichia coli bearing a mutation which confers the GlnC phenotype (inability to reduce the expression of glnA and other nitrogen-regulated operons in response to ammonia in the growth medium). A fragment of this DNA carrying glnA, the structural gene for glutamine synthetase, was cloned on plasmid pBR322. By using recombination in vitro, we mapped the GlnC mutation to a region between glnA and glnG. This region defines a gene, glnL, which codes for a trans-acting product; the GlnC mutant produces an altered product. The glnL product plays a key role in the communication of information concerning the quality and abundance of the nitrogen source in the growth medium to a destination responsible for the regulation of glnA and other genes for enzymes responsible for nitrogen utilization.