title: Ribonucleotide reductase of Escherichia coli. Cross-linking agents as probes of quaternary and quinary structure.
abstract: The quaternary structure of ribonucleotide reductase of Escherichia coli was investigated, with the use of purified B1 and B2 proteins and bifunctional cross-linking agents. The holoenzyme is known to be an alpha 2 beta 2 tetramer consisting of two dimeric proteins: B1 (alpha 2) and B2 (beta 2). The cross-linking data support a model in which both of the beta subunits interact closely with only one of the two alpha subunits. Some of the interactions involving B2 were localized to the C terminus of the protein by use of truncated B2 protein (beta',beta'), a proteolytic cleavage product of B2 in which the 30 carboxy-terminal residues are missing from each of the beta subunits. Other interactions were indicated by the ability of glutaredoxin, but not thioredoxin, to inhibit some of the cross-linking reactions. We also asked whether ribonucleotide reductase interacts closely with other proteins inside the cell, by adding cross-linkers directly to suspensions of whole bacteria. Proteins in extracts of these cross-linked bacteria were resolved electrophoretically and probed with a monoclonal antibody to the B1 protein. High-molecular-mass products were detected, supporting the utility of this method for identifying intracellular interactions among enzymes of DNA precursor biosynthesis.
authors.forename: C K
authors.initials: CK
authors.lastname: Mathews
authors.forename: B M
authors.initials: BM
authors.lastname: Sjöberg
authors.forename: P
authors.initials: P
authors.lastname: Reichard
mesh_terms: D003432:Cross-Linking Reagents / Q000494:pharmacology*; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics; D005796:Genes; D005798:Genes, Bacterial; D007700:Kinetics; D046911:Macromolecular Substances; D011487:Protein Conformation; D012264:Ribonucleotide Reductases / Q000235:genetics / Q000378:metabolism*
chemical_list: D003432:Cross-Linking Reagents; D046911:Macromolecular Substances; D012264:Ribonucleotide Reductases