Open AccessIsolation and characterization of the product of the methionine-regulatory gene metJ of Escherichia coli K-12.
Author(s) -
Albert A. Smith,
Ronald C. Greene,
Thomas W. Kirby,
Barbara Hindenach
Publication year - 1985
Publication title -
proceedings of the national academy of sciences of the united states of america
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.011
H-Index - 771
eISSN - 1091-6490
pISSN - 0027-8424
DOI - 10.1073/pnas.82.18.6104
Subject(s) - plasmid , gene , escherichia coli , dna , gene product , biology , biochemistry , chemistry , microbiology and biotechnology , genetics , gene expression
We have modified a previously isolated metJ plasmid by removing a segment of DNA including the rop gene. Bacterial strains carrying this plasmid produce elevated levels of the metJ gene product, presumably because of the high number of gene copies in the cell. We have isolated the metJ gene product in nearly homogeneous form from such a strain. The subunit size and the amino acid composition are the same as those predicted from the DNA sequence of the metJ gene. Sedimentation equilibrium measurements show that the native metJ gene product is a dimer. The purified dimer protects a short segment of DNA in the regulatory region of the metB and metJ genes from hydrolysis by DNase I.