Protein Structure and Folding
Get5 Carboxyl-terminal Domain Is a Novel Dimerization Motif That Tethers an Extended Get4/Get5 Complex*

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Tail-anchored trans-membrane proteins are targeted to membranes post-translationally. The proteins Get4 and Get5 form an obligate complex that catalyzes the transfer of tail-anchored proteins destined to the endoplasmic reticulum from Sgt2 to the cytosolic targeting factor Get3. Get5 forms a homodimer mediated by its carboxyl domain. We show here that a conserved motif exists within the carboxyl domain. A high resolution crystal structure and solution NMR structures of this motif reveal a novel and stable helical dimerization domain. We additionally determined a solution NMR structure of a divergent fungal homolog, and comparison of these structures allows annotation of specific stabilizing interactions. Using solution x-ray scattering and the structures of all folded domains, we present a model of the full-length Get4/Get5 complex.

Membrane Proteins
Nuclear Magnetic Resonance
Protein Structure
Protein Targeting
X-ray Crystallography
Get Pathway
Tail Anchor
Ubl4a

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Supported by National Institutes of Health Grant R01GM097572, the Searle Scholar program, and a Burroughs-Wellcome Fund career award for the biological sciences.

*

The Molecular Observatory at Caltech is supported by the Gordon and Betty Moore Foundation, the Beckman Institute, and the Sanofi-Aventis Bioengineering Research Program. Operations at SSRL are supported by the United States Department of Energy and the National Institutes of Health.

This article contains supplemental Tables 1 and 2 and Figs. S1–S5.