title: Activation of recA protein: the pitch of the helical complex with single-stranded DNA.
abstract: The complex of recA protein with single-stranded DNA in the presence of ATP is the active species in the three enzymatic activities of recA: the initiation of strand exchange, the hydrolysis of ATP and the cleavage of repressors. Here we find by cryo-electron microscopy of unstained and unfixed samples that the helical structure of the protein coat in this complex differs slightly but significantly from the structure in the complex with double-stranded DNA. We discuss how the larger pitch of the complex with single strands (100 +/- 2 A compared with 95 +/- 2 A with double strands) could contribute to its higher enzymatic activity.
authors.affiliation: Laboratoire de Biologie Structurale, CEA and CNRS URA 1333, DBMS/DSV, CENG, Grenoble, France.
authors.forename: E A
authors.initials: EA
authors.lastname: Hewat
authors.forename: R W
authors.initials: RW
authors.lastname: Ruigrok
authors.forename: E
authors.initials: E
authors.lastname: DiCapua
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D004269:DNA, Bacterial / Q000378:metabolism / Q000648:ultrastructure; D004277:DNA, Single-Stranded / Q000378:metabolism* / Q000648:ultrastructure; D006868:Hydrolysis; D008854:Microscopy, Electron; D009690:Nucleic Acid Conformation; D011487:Protein Conformation; D011938:Rec A Recombinases / Q000378:metabolism*
chemical_list: D004269:DNA, Bacterial; D004277:DNA, Single-Stranded; D000255:Adenosine Triphosphate; D011938:Rec A Recombinases