No abstract

A previously unmapped pan gene was localized in an Escherichia coli K-12 strain using Hfr and F' matings and by transduction studies. This Pan- mutation was shown by supplementation studies to impart a block in pantoate biosynthesis. The pan gene cotransduced with rha, metB, and argE placing it at 87 min.

The Pseudomonas aeruginosa tryptophan synthase genes, tipA and t7pB, which are induced by their substrate indoleglycerol phosphate, were cloned along with their controlling region into the BamHI site of pBR322 to produce the 10.7megadalton plasmid pZAZ5. Sall partial digestion and ligation yielded a smaller plasmid, pZAZ167, with the chromosomal insert reduced in size from 8.1 to 3.4 megadaltons. Both pZAZ5 and pZAZ167 display Pseudomonas-like regulation of the trpA and trpB genes. Deletion of an EcoRI fragment or a BgI fragment from pZAZ167 yielded plasmids pZAZ168 and pZAZ169; the former expresses trpB but not tipA, and the latter has lost both activities. A deleted form of pZAZ5 designated pZAZ1O1 was obtained by excising a BgllI-BamHI segment and religating the tip gene segment in the opposite orientation. This plasmid expresses t7pA and tipB constitutively. The physical maps of these plasmids establish the gene order: promoter-t7pB-trpA.