The Rad51/RadA N-Terminal Domain Activates Nucleoprotein Filament ATPase Activity

Department of Biochemistry and Molecular Genetics, University of Virginia, Box 800733, Charlottesville, Virginia 22908, USA.
Structure (Impact Factor: 6.79). 07/2006; 14(6):983-92. DOI: 10.1016/j.str.2006.04.001
Source: PubMed

ABSTRACT Proteins in the RecA/RadA/Rad51 family form helical filaments on DNA that function in homologous recombination. While these proteins all have the same highly conserved ATP binding core, the RadA/Rad51 proteins have an N-terminal domain that shows no homology with the C-terminal domain found in RecA. Both the Rad51 N-terminal and RecA C-terminal domains have been shown to bind DNA, but no role for these domains has been established. We show that RadA filaments can be trapped in either an inactive or active conformation with respect to the ATPase and that activation involves a large rotation of the subunit aided by the N-terminal domain. The G103E mutation within the yeast Rad51 N-terminal domain inactivates the filament by failing to make proper contacts between the N-terminal domain and the core. These results show that the N-terminal domains play a regulatory role in filament activation and highlight the modular architecture of the recombination proteins.

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Available from: Xiao-Ping Zhang, Jul 28, 2015
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    • "Besides, the RPA interaction region is located in the N terminal part of the protein (Residues 16 to 20) (Stauffer and Chazin, 2004), indicating possible species-specificity of this interaction region as well. The DNA binding domain is also located in the N terminal region; despite its variability, it is characterized by a G 103 (Galkin, 2006) that is conserved, as shown in the alignment (Fig. 2). "
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    • "However, it is difficult to envision how a regular and static nucleoprotein filament can go through the transitions required for recombination, which involve interaction with single-stranded DNA at initiation, three DNA strands during strand exchange and double-stranded DNA near completion of recombination. Not surprisingly, subsequent analyses of three-dimensional reconstructions from EM images and comparison with higher resolution crystal structures revealed structural variation among nucleoprotein filaments [21] [22] [23]. Most notably filament pitch varied considerably and could be correlated to status of bound nucleotide cofactor. "
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    • "exists within filaments of actin, called F-actin (for filamentous ) (Galkin et al., 2002b, 2001; Orlova and Egelman, 2000; Orlova et al., 1995; Egelman and DeRosier, 1991; Egelman et al., 1982). While F-actin might have been considered exceptional for having such structural plasticity, it now appears that it may be more typical, since other filaments , such as a bacterial type III secretion system polymer (Wang et al., 2006), the bacterial ParM filament (Orlova et al., 2007), the Rad51 recombination filament (Galkin et al., 2006b), an archaeal pilus (Wang et al., 2008) or the flagellar filament from Campylobacter jejuni (Galkin et al., 2008b), display a comparable or greater degree of variability. This heterogeneity and disorder poses great challenges for conventional methods of three-dimensional helical reconstruction (DeRosier and Klug, 1968), where it is necessary to assume that a polymer has a uniform helical symmetry which is imposed over long filaments. "
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