Removal of the RecA C-terminus results in a conformational change in the RecA-DNA filament.
The Escherichia coli RecA protein catalyzes homologous recombination of DNA molecules, and the active form of the protein is a helical polymer that it forms around DNA. Previous image analysis of electron micrographs has revealed the RecA protein to be organized into two domains or lobes within the RecA-DNA filament. We have now been able to show that a small modification of the RecA protein by proteolysis results in a significant shift in the internal mass in the RecA filament. We have cleaved approximately 18 residues from the C-terminus of the RecA protein, producing a roughly 36K MW RecA core protein that binds DNA and polymerizes normally. A three-dimensional reconstruction of this complex has been computed, and has been compared with a previous reconstruction of the intact protein. The main difference is consistent with a 15 A outward movement of the lobe that was at an inner radius in the wild-type protein. These observations yield additional evidence about the conformational flexibility of the RecA filament, and will aid in understanding the structural mechanics and dynamics of the RecA filament.
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Department of Cell Biology and Neuroanatomy, University of Minnesota Medical School, Minneapolis 55455.
Egelman
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EH
D000595:Amino Acid Sequence; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000648:ultrastructure; D007091:Image Processing, Computer-Assisted; D046911:Macromolecular Substances; D008969:Molecular Sequence Data; D010446:Peptide Fragments; D011487:Protein Conformation; D011938:Rec A Recombinases / Q000737:chemistry* / Q000648:ultrastructure; D011995:Recombination, Genetic / Q000502:physiology*; D013329:Structure-Activity Relationship
D004268:DNA-Binding Proteins; D046911:Macromolecular Substances; D010446:Peptide Fragments; D011938:Rec A Recombinases