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Novel disulfide bond-mediated dimerization of the CARD domain was revealed by the crystal structure of CARMA1 CARD.

Jang TH, Park JH, Park HH - PLoS ONE (2013)

Bottom Line: Despite the important role of the CARMA1 signalosome during lymphocyte activation and proliferation, limited structural information is available.Here, we report the dimeric structure of CARMA1 CARD at a resolution of 3.2 Å.Interestingly, although CARMA1 CARD has a canonical six helical-bundles structural fold similar to other CARDs, CARMA1 CARD shows the first homo-dimeric structure of CARD formed by a disulfide bond and reveals a possible biologically important homo-dimerization mechanism.

View Article: PubMed Central - PubMed

Affiliation: School of Biotechnology and Graduate School of Biochemistry at Yeungnam University, Gyeongsan, South Korea.

ABSTRACT
CARMA1, BCL10 and MALT1 form a large molecular complex known as the CARMA1 signalosome during lymphocyte activation. Lymphocyte activation via the CARMA1 signalosome is critical to immune response and linked to many immune diseases. Despite the important role of the CARMA1 signalosome during lymphocyte activation and proliferation, limited structural information is available. Here, we report the dimeric structure of CARMA1 CARD at a resolution of 3.2 Å. Interestingly, although CARMA1 CARD has a canonical six helical-bundles structural fold similar to other CARDs, CARMA1 CARD shows the first homo-dimeric structure of CARD formed by a disulfide bond and reveals a possible biologically important homo-dimerization mechanism.

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Crystal structure of CARMA1 CARD.A. Ribbon diagram of CARMA1 CARD. The chain from N- to C-termini is colored by the spectrum from blue to red. Helices from H1 to H6 are labeled. Missing residues are shown as a green dotted-line B. Dimer structure of CARMA1 CARD. Chain A (green color) and Chain B (cyan color) are shown separately. C. Structural comparison between monomeric CARMA1 CARD (colored in gray) and dimeric CARMA1 CARD (colored in green). D. Structure of NOD1 CARD.
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pone-0079778-g001: Crystal structure of CARMA1 CARD.A. Ribbon diagram of CARMA1 CARD. The chain from N- to C-termini is colored by the spectrum from blue to red. Helices from H1 to H6 are labeled. Missing residues are shown as a green dotted-line B. Dimer structure of CARMA1 CARD. Chain A (green color) and Chain B (cyan color) are shown separately. C. Structural comparison between monomeric CARMA1 CARD (colored in gray) and dimeric CARMA1 CARD (colored in green). D. Structure of NOD1 CARD.

Mentions: The 3.2 Å crystal structure of CARMA1 CARD was solved using a single-wavelength anomalous diffraction (SAD) method and refined to an Rwork of 29.1% and Rfree of 32.4%. The high resolution structure of CARMA1 CARD showed that it forms the canonical six-helical bundle fold comprising six helices, H1 to H6, which is characteristic of the DD superfamily (Figure 1A and 1B). There was one dimer in the asymmetric unit, referred to as chain A and chain B (Figure 1B). Model chains were built from residue 22 to residue 108. A flexible loop formed by residue 64 to residue 70 was missing from our model. The electron density of that region was too weak to trace, indicating that the loop is extraordinarily flexible relative to those of other CARD domains (Figure 1A and 1B). Chain A and Chain B formed a symmetric dimer. H3 and H6 were shorter than other helices. The N and C termini of CARMA1 CARD were located on the same side of the molecule. The six helices comprising residues 24-35, 39-49, 54-61, 73-83, 85-98, and 100-107 were numbered H1, H2, H3, H4, H5, and H6 (Figure 1A). Helix bundles tightly packed by a central hydrophobic core were formed by several conserved residues including V26, L33, I37, T43, I52, L76, L77, F92, L93, L95, and Y103 . This hydrophobic core supports the location of each helix and stabilizes the conformation of CARMA1 CARD. Three loops, including residues 36-38 (H1-H2 loop), 50-53 (H2-H3 loop), 62-72 (H3-H4 loop), and two linkers, including 84-85 (H4-H5 loop) and 99-100 (H5-H6 loop), connect the six helices. The missing H3-H4 loop was the longest loop. Interestingly, H1 of CARMA 1 CARD was bent in the middle. A bent H1 was previously detected in the structure of other CARDs including Apaf-1 CARD [33] and NOD1 CARD [34], but never in other death domain superfamily members, including DD, PYD and DED. These findings indicate that the bent H1 might be a distinct feature of the CARD subfamily. Recently, monomeric CARMA1 CARD structure was elucidated [35]. The RMSD value of superimposed structure between monomeric CARMA1 CARD and dimeric CARMA1 CARD was 0.7 Å indicating that the overall structure was almost identical (Figure 1C). The dimeric CARD was previously reported in the structure of NOD1 CARD [36]. In this structure, unusually extended sixth helix of NOD1 CARD is swapped between two monomers (Figure 1D).


Novel disulfide bond-mediated dimerization of the CARD domain was revealed by the crystal structure of CARMA1 CARD.

Jang TH, Park JH, Park HH - PLoS ONE (2013)

Crystal structure of CARMA1 CARD.A. Ribbon diagram of CARMA1 CARD. The chain from N- to C-termini is colored by the spectrum from blue to red. Helices from H1 to H6 are labeled. Missing residues are shown as a green dotted-line B. Dimer structure of CARMA1 CARD. Chain A (green color) and Chain B (cyan color) are shown separately. C. Structural comparison between monomeric CARMA1 CARD (colored in gray) and dimeric CARMA1 CARD (colored in green). D. Structure of NOD1 CARD.
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pone-0079778-g001: Crystal structure of CARMA1 CARD.A. Ribbon diagram of CARMA1 CARD. The chain from N- to C-termini is colored by the spectrum from blue to red. Helices from H1 to H6 are labeled. Missing residues are shown as a green dotted-line B. Dimer structure of CARMA1 CARD. Chain A (green color) and Chain B (cyan color) are shown separately. C. Structural comparison between monomeric CARMA1 CARD (colored in gray) and dimeric CARMA1 CARD (colored in green). D. Structure of NOD1 CARD.
Mentions: The 3.2 Å crystal structure of CARMA1 CARD was solved using a single-wavelength anomalous diffraction (SAD) method and refined to an Rwork of 29.1% and Rfree of 32.4%. The high resolution structure of CARMA1 CARD showed that it forms the canonical six-helical bundle fold comprising six helices, H1 to H6, which is characteristic of the DD superfamily (Figure 1A and 1B). There was one dimer in the asymmetric unit, referred to as chain A and chain B (Figure 1B). Model chains were built from residue 22 to residue 108. A flexible loop formed by residue 64 to residue 70 was missing from our model. The electron density of that region was too weak to trace, indicating that the loop is extraordinarily flexible relative to those of other CARD domains (Figure 1A and 1B). Chain A and Chain B formed a symmetric dimer. H3 and H6 were shorter than other helices. The N and C termini of CARMA1 CARD were located on the same side of the molecule. The six helices comprising residues 24-35, 39-49, 54-61, 73-83, 85-98, and 100-107 were numbered H1, H2, H3, H4, H5, and H6 (Figure 1A). Helix bundles tightly packed by a central hydrophobic core were formed by several conserved residues including V26, L33, I37, T43, I52, L76, L77, F92, L93, L95, and Y103 . This hydrophobic core supports the location of each helix and stabilizes the conformation of CARMA1 CARD. Three loops, including residues 36-38 (H1-H2 loop), 50-53 (H2-H3 loop), 62-72 (H3-H4 loop), and two linkers, including 84-85 (H4-H5 loop) and 99-100 (H5-H6 loop), connect the six helices. The missing H3-H4 loop was the longest loop. Interestingly, H1 of CARMA 1 CARD was bent in the middle. A bent H1 was previously detected in the structure of other CARDs including Apaf-1 CARD [33] and NOD1 CARD [34], but never in other death domain superfamily members, including DD, PYD and DED. These findings indicate that the bent H1 might be a distinct feature of the CARD subfamily. Recently, monomeric CARMA1 CARD structure was elucidated [35]. The RMSD value of superimposed structure between monomeric CARMA1 CARD and dimeric CARMA1 CARD was 0.7 Å indicating that the overall structure was almost identical (Figure 1C). The dimeric CARD was previously reported in the structure of NOD1 CARD [36]. In this structure, unusually extended sixth helix of NOD1 CARD is swapped between two monomers (Figure 1D).

Bottom Line: Despite the important role of the CARMA1 signalosome during lymphocyte activation and proliferation, limited structural information is available.Here, we report the dimeric structure of CARMA1 CARD at a resolution of 3.2 Å.Interestingly, although CARMA1 CARD has a canonical six helical-bundles structural fold similar to other CARDs, CARMA1 CARD shows the first homo-dimeric structure of CARD formed by a disulfide bond and reveals a possible biologically important homo-dimerization mechanism.

View Article: PubMed Central - PubMed

Affiliation: School of Biotechnology and Graduate School of Biochemistry at Yeungnam University, Gyeongsan, South Korea.

ABSTRACT
CARMA1, BCL10 and MALT1 form a large molecular complex known as the CARMA1 signalosome during lymphocyte activation. Lymphocyte activation via the CARMA1 signalosome is critical to immune response and linked to many immune diseases. Despite the important role of the CARMA1 signalosome during lymphocyte activation and proliferation, limited structural information is available. Here, we report the dimeric structure of CARMA1 CARD at a resolution of 3.2 Å. Interestingly, although CARMA1 CARD has a canonical six helical-bundles structural fold similar to other CARDs, CARMA1 CARD shows the first homo-dimeric structure of CARD formed by a disulfide bond and reveals a possible biologically important homo-dimerization mechanism.

Show MeSH
Related in: MedlinePlus