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2ebc
From Proteopedia
| 2ebc, resolution 2.24Å () | |||||||||
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| Related: | 1y3a, 2hlb, 1bof | ||||||||
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| Resources: | FirstGlance, OCA, PDBsum, RCSB | ||||||||
| Coordinates: | save as pdb, mmCIF, xml | ||||||||
Mechanism underlying the critical contribution of a switch II residue in a heterotrimeric G-protein alpha subunit during C. elegans asymmetric cell division
Heterotrimeric G-proteins are integral to a conserved regulatory module that influences metazoan asymmetric cell division (ACD). In the Caenorhabditis elegans zygote, GOA-1 (Galpha(o)) and GPA-16 (Galpha(i)) are involved in generating forces that pull on astral microtubules and position the spindle asymmetrically. GPA-16 function has been analyzed in vivo owing notably to a temperature-sensitive allele gpa-16(it143), which, at the restrictive temperature, results in spindle orientation defects in early embryos. Here we identify the structural basis of gpa-16(it143), which encodes a point mutation (G202D) in the switch II region of GPA-16. Using Galpha(i1)(G202D) as a model in biochemical analyses, we demonstrate that high temperature induces instability of the mutant Galpha. At the permissive temperature, the mutant Galpha was stable upon GTP binding, but switch II rearrangement was compromised, as were activation state-selective interactions with regulators involved in ACD, including GoLoco motifs, RGS proteins, and RIC-8. We solved the crystal structure of the mutant Galpha bound to GDP, which indicates a unique switch II conformation as well as steric constraints that suggest activated GPA-16(it143) is destabilized relative to wild type. Spindle severing in gpa-16(it143) embryos revealed that pulling forces are symmetric and markedly diminished at the restrictive temperature. Interestingly, pulling forces are asymmetric and generally similar in magnitude to wild type at the permissive temperature despite defects in the structure of GPA-16(it143). These normal pulling forces in gpa-16(it143) embryos at the permissive temperature were attributable to GOA-1 function, underscoring a complex interplay of Galpha subunit function in ACD.
Structural determinants underlying the temperature-sensitive nature of a Galpha mutant in asymmetric cell division of Caenorhabditis elegans., Johnston CA, Afshar K, Snyder JT, Tall GG, Gonczy P, Siderovski DP, Willard FS, J Biol Chem. 2008 Aug 1;283(31):21550-8. Epub 2008 Jun 2. PMID:18519563
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
About this Structure
2EBC is a 1 chain structure of sequence from Homo sapiens. Full crystallographic information is available from OCA.
Reference
- Johnston CA, Afshar K, Snyder JT, Tall GG, Gonczy P, Siderovski DP, Willard FS. Structural determinants underlying the temperature-sensitive nature of a Galpha mutant in asymmetric cell division of Caenorhabditis elegans. J Biol Chem. 2008 Aug 1;283(31):21550-8. Epub 2008 Jun 2. PMID:18519563 doi:10.1074/jbc.M803023200
Page seeded by OCA on Thu Sep 3 16:00:55 2009
