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The hexameric structures of human heat shock protein 90.

Lee CC, Lin TW, Ko TP, Wang AH - PLoS ONE (2011)

Bottom Line: HSP90 identified on the cell surface has been found to play a crucial role in cancer invasion and metastasis, and has become a validated anti-cancer target for drug development.The crystal structure of MC-HSP90 reveals that, in addition to the C-terminal dimerization domain, the residue W320 in the M domain plays a critical role in its oligomerization.This study not only demonstrates how the human MC-HSP90 forms a hexamer, but also justifies the similar formation of HSP90N by using 3D modeling analysis.

View Article: PubMed Central - PubMed

Affiliation: Institute of Biological Chemistry, Academia Sinica, Taipei, Taiwan.

ABSTRACT

Background: The human 90-kDa heat shock protein (HSP90) functions as a dimeric molecular chaperone. HSP90 identified on the cell surface has been found to play a crucial role in cancer invasion and metastasis, and has become a validated anti-cancer target for drug development. It has been shown to self-assemble into oligomers upon heat shock or divalent cations treatment, but the functional role of the oligomeric states in the chaperone cycle is not fully understood.

Principal findings: Here we report the crystal structure of a truncated HSP90 that contains the middle segment and the carboxy-terminal domain, termed MC-HSP90. The structure reveals an architecture with triangular bipyramid geometry, in which the building block of the hexameric assembly is a dimer. In solution, MC-HSP90 exists in three major oligomer states, namely dimer, tetramer and hexamer, which were elucidated by size exclusion chromatography and analytical ultracentrifugation. The newly discovered HSP90 isoform HSP90N that lacks the N-terminal ATPase domain also exhibited similar oligomerization states as did MC-HSP90.

Conclusions: While lacking the ATPase domain, both MC-HSP90 and HSP90N can self-assemble into a hexameric structure, spontaneously. The crystal structure of MC-HSP90 reveals that, in addition to the C-terminal dimerization domain, the residue W320 in the M domain plays a critical role in its oligomerization. This study not only demonstrates how the human MC-HSP90 forms a hexamer, but also justifies the similar formation of HSP90N by using 3D modeling analysis.

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MC-HSP90 assembly and models of HSP90N hexamer.(A) Assembly of MC-HSP90 hexameric structure. The process begins with a monomer (orange) subunit associating with another monomer (green) to form a stable dimer as the building block. It continues with further association of dimers via the N-terminal interface of M domain to form a possible dimer of dimers (or tetramer) and a stable hexamer. The occurrence of tetramer might represent an intermediate. In the models of MC-HSP90 dimer, tetramer and hexamer shown here, the building blocks are paired and indicated by the labels AA′, BB′ and CC′. (B) Top view and side view of HSP90N hexamer with 12 flexible polypeptide segments hanging around the core structure. The protomers of hexameric HSP90N are represented by different colors, green, orange, blue, yellow, red, and megenta. The N-terminal hydrophilic extension and C-terminal tail of the yellow protomer are labeled.
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pone-0019961-g007: MC-HSP90 assembly and models of HSP90N hexamer.(A) Assembly of MC-HSP90 hexameric structure. The process begins with a monomer (orange) subunit associating with another monomer (green) to form a stable dimer as the building block. It continues with further association of dimers via the N-terminal interface of M domain to form a possible dimer of dimers (or tetramer) and a stable hexamer. The occurrence of tetramer might represent an intermediate. In the models of MC-HSP90 dimer, tetramer and hexamer shown here, the building blocks are paired and indicated by the labels AA′, BB′ and CC′. (B) Top view and side view of HSP90N hexamer with 12 flexible polypeptide segments hanging around the core structure. The protomers of hexameric HSP90N are represented by different colors, green, orange, blue, yellow, red, and megenta. The N-terminal hydrophilic extension and C-terminal tail of the yellow protomer are labeled.

Mentions: Based on the observed 3D structure of MC-HSP90 determined in the P21 crystal, the sedimentation coefficient values of MC-HSP90 at dimer and each oligomer states were calculated by using the computer program HYDROPRO [22], and compared with the experimental values from the sedimentation velocity experiments. As shown in Figure 7A, the atomic models of monomer, dimer, tetramer and hexamer yielded sedimentation coefficients of 3.7S, 5.7S, 8.8S and 11.9S, respectively. These HYDROPRO predicted S values for MC-HSP90 dimer, tetramer and hexamer models were similar to the experimental results (Table 2). The agreement between the calculated and experimental values confirms the existance of MC-HSP90 in these oligomeric states. Furthermore, during the gel-filtration separation and sedimentation velocity experiments, the MC-HSP90 oligomers did not undergo rapid interconversion between one another. Otherwise the redistribution of protein in different states would result in similar pattern of the sedimentation velocity profiles, for some equilibrium state. It indicates that the association and dissociation between each state is irreversible or the equilibrium rate is very slow due to large energy barriers.


The hexameric structures of human heat shock protein 90.

Lee CC, Lin TW, Ko TP, Wang AH - PLoS ONE (2011)

MC-HSP90 assembly and models of HSP90N hexamer.(A) Assembly of MC-HSP90 hexameric structure. The process begins with a monomer (orange) subunit associating with another monomer (green) to form a stable dimer as the building block. It continues with further association of dimers via the N-terminal interface of M domain to form a possible dimer of dimers (or tetramer) and a stable hexamer. The occurrence of tetramer might represent an intermediate. In the models of MC-HSP90 dimer, tetramer and hexamer shown here, the building blocks are paired and indicated by the labels AA′, BB′ and CC′. (B) Top view and side view of HSP90N hexamer with 12 flexible polypeptide segments hanging around the core structure. The protomers of hexameric HSP90N are represented by different colors, green, orange, blue, yellow, red, and megenta. The N-terminal hydrophilic extension and C-terminal tail of the yellow protomer are labeled.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3102065&req=5

pone-0019961-g007: MC-HSP90 assembly and models of HSP90N hexamer.(A) Assembly of MC-HSP90 hexameric structure. The process begins with a monomer (orange) subunit associating with another monomer (green) to form a stable dimer as the building block. It continues with further association of dimers via the N-terminal interface of M domain to form a possible dimer of dimers (or tetramer) and a stable hexamer. The occurrence of tetramer might represent an intermediate. In the models of MC-HSP90 dimer, tetramer and hexamer shown here, the building blocks are paired and indicated by the labels AA′, BB′ and CC′. (B) Top view and side view of HSP90N hexamer with 12 flexible polypeptide segments hanging around the core structure. The protomers of hexameric HSP90N are represented by different colors, green, orange, blue, yellow, red, and megenta. The N-terminal hydrophilic extension and C-terminal tail of the yellow protomer are labeled.
Mentions: Based on the observed 3D structure of MC-HSP90 determined in the P21 crystal, the sedimentation coefficient values of MC-HSP90 at dimer and each oligomer states were calculated by using the computer program HYDROPRO [22], and compared with the experimental values from the sedimentation velocity experiments. As shown in Figure 7A, the atomic models of monomer, dimer, tetramer and hexamer yielded sedimentation coefficients of 3.7S, 5.7S, 8.8S and 11.9S, respectively. These HYDROPRO predicted S values for MC-HSP90 dimer, tetramer and hexamer models were similar to the experimental results (Table 2). The agreement between the calculated and experimental values confirms the existance of MC-HSP90 in these oligomeric states. Furthermore, during the gel-filtration separation and sedimentation velocity experiments, the MC-HSP90 oligomers did not undergo rapid interconversion between one another. Otherwise the redistribution of protein in different states would result in similar pattern of the sedimentation velocity profiles, for some equilibrium state. It indicates that the association and dissociation between each state is irreversible or the equilibrium rate is very slow due to large energy barriers.

Bottom Line: HSP90 identified on the cell surface has been found to play a crucial role in cancer invasion and metastasis, and has become a validated anti-cancer target for drug development.The crystal structure of MC-HSP90 reveals that, in addition to the C-terminal dimerization domain, the residue W320 in the M domain plays a critical role in its oligomerization.This study not only demonstrates how the human MC-HSP90 forms a hexamer, but also justifies the similar formation of HSP90N by using 3D modeling analysis.

View Article: PubMed Central - PubMed

Affiliation: Institute of Biological Chemistry, Academia Sinica, Taipei, Taiwan.

ABSTRACT

Background: The human 90-kDa heat shock protein (HSP90) functions as a dimeric molecular chaperone. HSP90 identified on the cell surface has been found to play a crucial role in cancer invasion and metastasis, and has become a validated anti-cancer target for drug development. It has been shown to self-assemble into oligomers upon heat shock or divalent cations treatment, but the functional role of the oligomeric states in the chaperone cycle is not fully understood.

Principal findings: Here we report the crystal structure of a truncated HSP90 that contains the middle segment and the carboxy-terminal domain, termed MC-HSP90. The structure reveals an architecture with triangular bipyramid geometry, in which the building block of the hexameric assembly is a dimer. In solution, MC-HSP90 exists in three major oligomer states, namely dimer, tetramer and hexamer, which were elucidated by size exclusion chromatography and analytical ultracentrifugation. The newly discovered HSP90 isoform HSP90N that lacks the N-terminal ATPase domain also exhibited similar oligomerization states as did MC-HSP90.

Conclusions: While lacking the ATPase domain, both MC-HSP90 and HSP90N can self-assemble into a hexameric structure, spontaneously. The crystal structure of MC-HSP90 reveals that, in addition to the C-terminal dimerization domain, the residue W320 in the M domain plays a critical role in its oligomerization. This study not only demonstrates how the human MC-HSP90 forms a hexamer, but also justifies the similar formation of HSP90N by using 3D modeling analysis.

Show MeSH
Related in: MedlinePlus