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. 2011 Jan;2(1):27-30.
doi: 10.4161/sgtp.2.1.14938.

GTP-dependent scaffold formation in the GTPase of Immunity Associated Protein family

David Schwefel  1 , Oliver Daumke
Affiliations

GTP-dependent scaffold formation in the GTPase of Immunity Associated Protein family

David Schwefel et al. Small GTPases. 2011 Jan.

Abstract

GTP ases of Immunity-Associated Proteins (GIMAPs) are a family of guanine nucleotide binding (G) proteins which are implicated in the regulation of apoptosis in lymphocytes. GIMAPs are composed of an amino-terminal G domain and carboxy-terminal extensions of varying size. Our recent biochemical and structural analysis of a representative GIMAP family member, GIMAP2, revealed the molecular basis of GTP-dependent oligomerization which involves two interfaces in the G domain. Whereas the amphipathic helix α7 in the C-terminal extension closely folds against the G domain in the GDP-bound state, it might be released in the GTP-bound state to assemble interaction partners. We also showed that the GIMAP2 oligomer functions at the surface of lipid droplets in a Jurkat T cell line. Here, we review our recent work and discuss the GIMAP2 oligomer as a GTP-dependent protein scaffold at the surface of lipid droplets controlling apoptosis.

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Figures

Figure 1
Figure 1
GTP-dependent scaffold formation of GIMAP2. (upper part) The structure of the monomeric nucleotide-free GIMAP2 shows a Ras-like G-domain (in green). Additional secondary structure elements compared to the minimal Ras G-domain are helix α3* and the two amphipathic helices α6 and α7 (in orange), which fold against switch II (blue). (lower part) In the absence of α7 and the presence of GTP, GIMAP2 oligomerized via two interfaces in the crystal to form a linear oligomer (the direction of the oligomerization axis is indicated by the black arrows). The conversion between the monomeric and oligomeric states is regulated by GTP binding or hydrolysis (red arrows).
See this image and copyright information in PMC

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