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NarL dimerization? Suggestive evidence from a new crystal form
I Baikalov1, I Schröder, M Kaczor-Grzeskowiak
1Molecular Biology Institute, University of California, Los Angeles 90095-1570, USA.
Biochemistry
|April 2, 1998
Summary
Structural analysis of the Escherichia coli NarL protein reveals its N and C domains pair correctly and confirms the "telephone receiver" model for DNA binding activation. Monomer dimerization may also play a role in DNA interaction.
Area of Science:
- Molecular Biology
- Structural Biology
- Biochemistry
Background:
- The response regulator NarL in Escherichia coli controls gene expression in response to nitrate and nitrite.
- Understanding NarL's structure is crucial for elucidating bacterial regulatory mechanisms.
Purpose of the Study:
- To determine the high-resolution crystal structure of NarL in a new monoclinic space group.
- To compare this new structure with the existing orthorhombic structure to gain insights into NarL's conformational states and activation mechanism.
Main Methods:
- X-ray crystallography to solve the structure of NarL in a monoclinic crystal form.
- Comparative structural analysis of three independent NarL molecules (two monoclinic, one orthorhombic).
Main Results:
- Confirmed the correct pairing of NarL's N and C domains, with only a minor gap in visibility.
- Demonstrated that crystal packing effects on NarL structure are negligible.
- Validated the "telephone receiver" model for NarL activation, where N-domain displacement is necessary for DNA binding.
- Observed a strong tendency for NarL monomers to dimerize via alpha 1 helix contacts, suggesting a role in DNA binding.
Conclusions:
- The crystal structures provide three independent snapshots of NarL, confirming domain arrangement and activation mechanism.
- NarL dimerization through alpha 1 helix interactions may be mechanistically significant for DNA binding, similar to other related proteins.