Abstract
A recombinant plasmid, designated pMu leu1, was constructed from Mucor racemosus genomic DNA and Escherichia coli plasmid pBR322. This plasmid complemented the leuB6 mutation of E. coli, apparently by suppression. The plasmid contained two HindIII fragments of approximately 3.0 and 1.7 kilobases. Neither fragment alone exhibited complementing activity. Several proteins were specified by the plasmid, but their role, if any, in complementation is unknown.