Selection by genetic complementation and characterization of the gene coding for the XXXX porphobilinogen deaminase.

@entity5068 @entity375 @entity72211 @entity844
The porphobilinogen deaminase (PBG-D) gene of @entity375 has been isolated by genetic complementation of a mutant GL7 (alpha @entity72211 ) strain, previously shown to be defective in this haembiosynthetic enzyme [Gollub, Liu, Dayan, Adlersberg _ Sprinson (1977) J. Biol. Chem. 252, 2846-2854]. The gene was selected from a @entity375 wild-type genomic DNA library ligated into the shuttle vector YEp13. The complementing gene restored growth of the @entity72211 (PBG-D) mutant strain on media in the absence of exogeneous haem or @entity844 and @entity5068 supplements. The recombinant plasmid was retained in the Hem+ transformant provided that selective pressure for plasmid-dependent growth was maintained. Transformation of the mutant strain ( @entity72211 ) restored the PBG-D activity to levels up to 10-fold those of the parental strain. The mutant strain GL7 does not show any measurable enzymic activity. Analysis of the plasmid designated YEpPBG-D (containing the PBG-D gene) by hybrid-selected translation revealed that it contained the coding information for a single protein of apparent Mr 43,000. The coding region was localized on an 1.5 kb endonuclease-EcoRI fragment (E4), within the 5.5 kb genomic insert in YEpPBG-D.
