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Structural basis for ESCRT-III protein autoinhibition.

Bajorek M, Schubert HL, McCullough J, Langelier C, Eckert DM, Stubblefield WM, Uter NT, Myszka DG, Hill CP, Sundquist WI - Nat. Struct. Mol. Biol. (2009)

Bottom Line: Here we show that the N-terminal core domains of increased sodium tolerance-1 (IST1) and charged multivesicular body protein-3 (CHMP3) form equivalent four-helix bundles, revealing that IST1 is a previously unrecognized ESCRT-III family member.The IST1 and CHMP3 structures also reveal that equivalent downstream alpha5 helices can fold back against the core domains.Mutations within the CHMP3 core-alpha5 interface stimulate the protein's in vitro assembly and HIV-inhibition activities, indicating that dissociation of the autoinhibitory alpha5 helix from the core activates ESCRT-III proteins for assembly at membranes.

View Article: PubMed Central - PubMed

Affiliation: Department of Biochemistry, University of Utah, Salt Lake City, Utah, USA.

ABSTRACT
Endosomal sorting complexes required for transport-III (ESCRT-III) subunits cycle between two states: soluble monomers and higher-order assemblies that bind and remodel membranes during endosomal vesicle formation, midbody abscission and enveloped virus budding. Here we show that the N-terminal core domains of increased sodium tolerance-1 (IST1) and charged multivesicular body protein-3 (CHMP3) form equivalent four-helix bundles, revealing that IST1 is a previously unrecognized ESCRT-III family member. IST1 and its ESCRT-III binding partner, CHMP1B, both form higher-order helical structures in vitro, and IST1-CHMP1 interactions are required for abscission. The IST1 and CHMP3 structures also reveal that equivalent downstream alpha5 helices can fold back against the core domains. Mutations within the CHMP3 core-alpha5 interface stimulate the protein's in vitro assembly and HIV-inhibition activities, indicating that dissociation of the autoinhibitory alpha5 helix from the core activates ESCRT-III proteins for assembly at membranes.

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CHMP3 crystal packing interactions. (a) Overlay of the cores of the “tip-to-tip” dimers in the crystal lattices of CHMP38–183 (orange)16 and CHMP38–222 (blue and green). The upper subunits were aligned, and the lower subunits diverge owing to small differences in their tip-to-tip interfaces. (b) Detailed expansion of the boxed region of CHMP38–222 shown in a. Both here and in e, most side chains conformations are shown as defined in the CHMP38–183 search model, with some minor adjustments to avoid clashes. Precise description of these side chain conformations is not possible at current resolutions. (c) Subunit packing down the 31 screw axis of the CHMP31–150 crystal lattice, with a single CHMP31–150 molecule highlighted in blue. (d) Same assembly as in c, but viewed perpendicularly to the 31 screw axis. (e) Detailed expansion of the boxed area shown in d.
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Figure 3: CHMP3 crystal packing interactions. (a) Overlay of the cores of the “tip-to-tip” dimers in the crystal lattices of CHMP38–183 (orange)16 and CHMP38–222 (blue and green). The upper subunits were aligned, and the lower subunits diverge owing to small differences in their tip-to-tip interfaces. (b) Detailed expansion of the boxed region of CHMP38–222 shown in a. Both here and in e, most side chains conformations are shown as defined in the CHMP38–183 search model, with some minor adjustments to avoid clashes. Precise description of these side chain conformations is not possible at current resolutions. (c) Subunit packing down the 31 screw axis of the CHMP31–150 crystal lattice, with a single CHMP31–150 molecule highlighted in blue. (d) Same assembly as in c, but viewed perpendicularly to the 31 screw axis. (e) Detailed expansion of the boxed area shown in d.

Mentions: Two of the new CHMP3 interfaces merit comment because they are mediated by a conserved, exposed hydrophobic surface on the closed “tip” of the α1/α2 hairpin. In the CHMP8–222 structure, two adjacent molecules associate through a small (359 Å2) two-fold symmetric “tip-to-tip” dimer interface (Fig. 3a,b). A similar tip-to-tip interface was also present in the CHMP38–183 lattice16, and this is the only interface that has been seen in more than one crystal form.


Structural basis for ESCRT-III protein autoinhibition.

Bajorek M, Schubert HL, McCullough J, Langelier C, Eckert DM, Stubblefield WM, Uter NT, Myszka DG, Hill CP, Sundquist WI - Nat. Struct. Mol. Biol. (2009)

CHMP3 crystal packing interactions. (a) Overlay of the cores of the “tip-to-tip” dimers in the crystal lattices of CHMP38–183 (orange)16 and CHMP38–222 (blue and green). The upper subunits were aligned, and the lower subunits diverge owing to small differences in their tip-to-tip interfaces. (b) Detailed expansion of the boxed region of CHMP38–222 shown in a. Both here and in e, most side chains conformations are shown as defined in the CHMP38–183 search model, with some minor adjustments to avoid clashes. Precise description of these side chain conformations is not possible at current resolutions. (c) Subunit packing down the 31 screw axis of the CHMP31–150 crystal lattice, with a single CHMP31–150 molecule highlighted in blue. (d) Same assembly as in c, but viewed perpendicularly to the 31 screw axis. (e) Detailed expansion of the boxed area shown in d.
© Copyright Policy
Related In: Results  -  Collection

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Figure 3: CHMP3 crystal packing interactions. (a) Overlay of the cores of the “tip-to-tip” dimers in the crystal lattices of CHMP38–183 (orange)16 and CHMP38–222 (blue and green). The upper subunits were aligned, and the lower subunits diverge owing to small differences in their tip-to-tip interfaces. (b) Detailed expansion of the boxed region of CHMP38–222 shown in a. Both here and in e, most side chains conformations are shown as defined in the CHMP38–183 search model, with some minor adjustments to avoid clashes. Precise description of these side chain conformations is not possible at current resolutions. (c) Subunit packing down the 31 screw axis of the CHMP31–150 crystal lattice, with a single CHMP31–150 molecule highlighted in blue. (d) Same assembly as in c, but viewed perpendicularly to the 31 screw axis. (e) Detailed expansion of the boxed area shown in d.
Mentions: Two of the new CHMP3 interfaces merit comment because they are mediated by a conserved, exposed hydrophobic surface on the closed “tip” of the α1/α2 hairpin. In the CHMP8–222 structure, two adjacent molecules associate through a small (359 Å2) two-fold symmetric “tip-to-tip” dimer interface (Fig. 3a,b). A similar tip-to-tip interface was also present in the CHMP38–183 lattice16, and this is the only interface that has been seen in more than one crystal form.

Bottom Line: Here we show that the N-terminal core domains of increased sodium tolerance-1 (IST1) and charged multivesicular body protein-3 (CHMP3) form equivalent four-helix bundles, revealing that IST1 is a previously unrecognized ESCRT-III family member.The IST1 and CHMP3 structures also reveal that equivalent downstream alpha5 helices can fold back against the core domains.Mutations within the CHMP3 core-alpha5 interface stimulate the protein's in vitro assembly and HIV-inhibition activities, indicating that dissociation of the autoinhibitory alpha5 helix from the core activates ESCRT-III proteins for assembly at membranes.

View Article: PubMed Central - PubMed

Affiliation: Department of Biochemistry, University of Utah, Salt Lake City, Utah, USA.

ABSTRACT
Endosomal sorting complexes required for transport-III (ESCRT-III) subunits cycle between two states: soluble monomers and higher-order assemblies that bind and remodel membranes during endosomal vesicle formation, midbody abscission and enveloped virus budding. Here we show that the N-terminal core domains of increased sodium tolerance-1 (IST1) and charged multivesicular body protein-3 (CHMP3) form equivalent four-helix bundles, revealing that IST1 is a previously unrecognized ESCRT-III family member. IST1 and its ESCRT-III binding partner, CHMP1B, both form higher-order helical structures in vitro, and IST1-CHMP1 interactions are required for abscission. The IST1 and CHMP3 structures also reveal that equivalent downstream alpha5 helices can fold back against the core domains. Mutations within the CHMP3 core-alpha5 interface stimulate the protein's in vitro assembly and HIV-inhibition activities, indicating that dissociation of the autoinhibitory alpha5 helix from the core activates ESCRT-III proteins for assembly at membranes.

Show MeSH
Related in: MedlinePlus