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Title: A Rac1--GDP trimer complex binds zinc with tetrahedral and octahedral coordination, displacing magnesium

Abstract

The Rho family of small GTPases represent well characterized signaling molecules that regulate many cellular functions such as actin cytoskeletal arrangement and the cell cycle by acting as molecular switches. A Rac1-GDP-Zn complex has been crystallized in space group P3221 and its crystal structure has been solved at 1.9 {angstrom} resolution. These trigonal crystals reveal the unexpected ability of Rac1 to coordinate Zn atoms in a tetrahedral fashion by use of its biologically relevant switch I and switch II regions. Upon coordination of zinc, the switch I region is stabilized in the GDP-bound conformation and contributes to a Rac1 trimer in the asymmetric unit. Zinc coordination causes switch II to adopt a novel conformation with a symmetry-related molecule. Additionally, zinc was found to displace magnesium from its octahedral coordination at switch I, although GDP binding remained stable. This structure represents the first reported Rac1-GDP-Zn complex, which further underscores the conformational flexibility and versatility of the small GTPase switch regions.

Authors:
;
Publication Date:
Research Org.:
Brookhaven National Laboratory (BNL) National Synchrotron Light Source
Sponsoring Org.:
Doe - Office Of Science
OSTI Identifier:
979987
Report Number(s):
BNL-92905-2010-JA
TRN: US201015%%1372
DOE Contract Number:
DE-AC02-98CH10886
Resource Type:
Journal Article
Resource Relation:
Journal Name: Acta Crystallographica Section D: Biological Crystallography; Journal Volume: 63
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 59 BASIC BIOLOGICAL SCIENCES; 99 GENERAL AND MISCELLANEOUS//MATHEMATICS, COMPUTING, AND INFORMATION SCIENCE; ACTIN; ATOMS; CELL CYCLE; COORDINATES; CRYSTAL STRUCTURE; CRYSTALS; FLEXIBILITY; FUNCTIONS; MAGNESIUM; MOLECULES; RESOLUTION; SPACE GROUPS; SWITCHES; USA; USES; WELLS; ZINC; national synchrotron light source

Citation Formats

Prehna, G., and Stebbins, C. A Rac1--GDP trimer complex binds zinc with tetrahedral and octahedral coordination, displacing magnesium. United States: N. p., 2007. Web. doi:10.1107/S0907444907010888.
Prehna, G., & Stebbins, C. A Rac1--GDP trimer complex binds zinc with tetrahedral and octahedral coordination, displacing magnesium. United States. doi:10.1107/S0907444907010888.
Prehna, G., and Stebbins, C. Mon . "A Rac1--GDP trimer complex binds zinc with tetrahedral and octahedral coordination, displacing magnesium". United States. doi:10.1107/S0907444907010888.
@article{osti_979987,
title = {A Rac1--GDP trimer complex binds zinc with tetrahedral and octahedral coordination, displacing magnesium},
author = {Prehna, G. and Stebbins, C},
abstractNote = {The Rho family of small GTPases represent well characterized signaling molecules that regulate many cellular functions such as actin cytoskeletal arrangement and the cell cycle by acting as molecular switches. A Rac1-GDP-Zn complex has been crystallized in space group P3221 and its crystal structure has been solved at 1.9 {angstrom} resolution. These trigonal crystals reveal the unexpected ability of Rac1 to coordinate Zn atoms in a tetrahedral fashion by use of its biologically relevant switch I and switch II regions. Upon coordination of zinc, the switch I region is stabilized in the GDP-bound conformation and contributes to a Rac1 trimer in the asymmetric unit. Zinc coordination causes switch II to adopt a novel conformation with a symmetry-related molecule. Additionally, zinc was found to displace magnesium from its octahedral coordination at switch I, although GDP binding remained stable. This structure represents the first reported Rac1-GDP-Zn complex, which further underscores the conformational flexibility and versatility of the small GTPase switch regions.},
doi = {10.1107/S0907444907010888},
journal = {Acta Crystallographica Section D: Biological Crystallography},
number = ,
volume = 63,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}
  • The Rho family of small GTPases represent well characterized signaling molecules that regulate many cellular functions such as actin cytoskeletal arrangement and the cell cycle by acting as molecular switches. A Rac1-GDP-Zn complex has been crystallized in space group P3{sub 2}21 and its crystal structure has been solved at 1.9 {angstrom} resolution. These trigonal crystals reveal the unexpected ability of Rac1 to coordinate Zn atoms in a tetrahedral fashion by use of its biologically relevant switch I and switch II regions. Upon coordination of zinc, the switch I region is stabilized in the GDP-bound conformation and contributes to a Rac1more » trimer in the asymmetric unit. Zinc coordination causes switch II to adopt a novel conformation with a symmetry-related molecule. Additionally, zinc was found to displace magnesium from its octahedral coordination at switch I, although GDP binding remained stable. This structure represents the first reported Rac1-GDP-Zn complex, which further underscores the conformational flexibility and versatility of the small GTPase switch regions.« less
  • We used the JUMBO monochromator at SSRL to measure the Al K-edge X-ray absorption spectra of synthetic micas having variable Al content and occupancy, from 0 to 2/3 in the octahedral M positions, and 0 to 2/3 in the tetrahedral T positions. The measured Al K edges differ markedly, but the differences may have a common explanation: (1) Micas containing 1/3 Al in M or {1/4} Al in T have K edges that differ in the energy and intensity of the first two features, which are related to interaction of Al with its first-shell nearest neighbors (O and OH ormore » F). They are nearly identical to the K edges of reference minerals such as albite (tetrahedral Al only) or grossular (octahedral Al only). (2) Micas containing Al in both M and T have K edges that can be interpreted as a weighed combination of the simple edges. 39 refs., 4 figs., 1 tab.« less
  • The equilibrium oct(CoCl₂Py₄) = tet(CoCl₂Py₂) + 2 Py for cobaltous chloride solutions in pyridine is followed over a temperature range, yielding DELTA H = 13.4 kcal/mole. At 38 deg C the equilibrium constant is estimated as (CoPy₂Cl₂) (Py)₂/(CoCl₂Py₄) = 0.04, and the DELTA S for the reaction is about 36.7 eu. It is pointed out that the average bond strength in the tetrahedral species is about 17 kcal greater than for the same groups in the octahedral configuration, and that the strength of binding and the dissociation energy for the two ligands released according to the equation above are significantmore » factors in determining the equilibrium reaction. Detailed arguments are given against the view that the relative stability of octahedrally and tetrahedrally coordinated complexes, such as the pair discussed, reflect principally the difference in "ligand-field stabilization" of the nonbonding d electrons between octahedral and tetrahedral fields. (auth)« less
  • No abstract prepared.