Quaternary polymorphism of replicative helicase G40P: structural mapping and domain rearrangement.
Quaternary polymorphism is a distinctive structural feature of the DnaB family of replicative DNA hexameric helicases. The Bacillus subtilis bacteriophage SPP1 gene 40 product (G40P) belongs to this family. Three different quaternary states have been described for G40P homohexamers, two of them with C(3) symmetry, and the other with C(6) symmetry. We present three-dimensional reconstructions of the different architectures of G40P hexamers and a variant lacking the N-terminal domain. Comparison of the G40P and the deletion mutant structures sheds new light on the functional roles of the N and C-terminal domains, at the same time that it allows the direct structural mapping of these domains. Based on this new information, hybrid EM/X-ray models are presented for all the different symmetries. These results suggest that quaternary polymorphism of hexameric helicases may be implicated in the translocation along the DNA.
Department of Macro-molecular Structure, Centro Nacional de Biotecnología, CSIC, Campus Universidad Autónoma de Madrid, 28049 Cantoblanco, Madrid, Spain.
Rafael
R
Núñez-Ramírez
Yolanda
Y
Robledo
Pablo
P
Mesa
Silvia
S
Ayora
Juan Carlos
JC
Alonso
José María
JM
Carazo
Luis Enrique
LE
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D000595:Amino Acid Sequence; D004265:DNA Helicases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism / Q000648:ultrastructure; D008958:Models, Molecular; D008969:Molecular Sequence Data; D020033:Protein Isoforms / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism / Q000648:ultrastructure; D020836:Protein Structure, Quaternary; D016415:Sequence Alignment; D014764:Viral Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism / Q000648:ultrastructure
D020033:Protein Isoforms; D014764:Viral Proteins; D004265:DNA Helicases; C115901:G40P helicase protein, Bacteriophage SPP1