Structure of the Inhibited Smooth Muscle Myosin and Its Implications on the Regulation of Insect Striated Muscle Myosin

Figures

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  Figure 1. Schematic drawing of the conformational transition of SmM and the 3D structure of the IHM of shutdown SmM. The left panel shows the conformational transition between the 6S active state and the 10S shutdown state of smooth muscle myosin. The right panel is the entire folded molecule showing IHM and the folded tail (PDB ID: 7MF3, 3.4 Å). Color code: light blue, blocked head; gray, free head; light gray, tail; light green, ELC; light pink, RLC.

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  Figure 2. Diagram of the Drosophila Mhc gene and the structure of Drosophila myosin-2. (A) Diagram of the Drosophila Mhc gene, showing the exon–intron structure. Constitutive exons are colored in black, and alternative exons are colored. The exon usage of typical isoforms, such as embryonic muscle myosin (3a/7a/9b/11c) and indirect flight muscle myosin (3b/7d/9a/11e), is displayed. (B) Crystal structure of the Drosophila myosin-2 motor domain (PDB ID: 5W1A, 2.23 Å), exhibiting the alternative exon usage in embryonic muscle myosin (3a/7a/9b/11c) and indirect flight muscle myosin (3b/7d/9a/11e). The alternative regions in the structure are color-coded to correspond to the exons in the Drosophila Mhc gene. Color code: gray, motor head; light green, ELC; blue, exon 3 (N-SH3); green, exon 7 (ATP-lip); magenta, exon 9 (relay); orange, exon 11 (converter).

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  Figure 3. Localization and interactions of the four alternative regions in the motor domain of Drosophila MHC. (A) Structure of the IHM of shutdown myosin-2, highlighting the location and the interactions of the four alternative regions. Color code: light blue, blocked head; gray, free head; light gray, the tail; light green, ELCs; light pink, RLCs; blue, exon 3 (N-SH3); green, exon 7 (ATP-lip); magenta, exon 9 (relay); orange, exon 11 (converter). (B) Summary of interactions involving the alternative regions in the IHM.

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  Figure 4. Amino acid sequence and interaction analyses of exon 3 encoding region. (A) Amino acid sequence alignment of chicken smooth muscle myosin and Drosophila MHC in the regions encoded by the alternative exon 3 of the Drosophila Mhc gene. The red arrows indicate the amino acids in BH exon 3 that are involved in stabilizing the IHM. (B) Interactions between the BH N-SH3 and segment 2. The color coding is consistent with Figure 3.

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  Figure 5. Amino acid sequence and interaction analyses of exon 7 encoding region. (A) Amino acid sequence alignment of chicken smooth muscle myosin and Drosophila MHC in the regions encoded by alternative exon 7 of the Drosophila Mhc gene. The red arrow indicates the amino acid in BH exon 7 involved in stabilizing the IHM. (B) Interaction between the BH ATP-lip and the FH converter. The color coding is consistent with Figure 3.

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  Figure 6. Amino acid sequence and interaction analyses of exon 9 encoding region. (A) Amino acid sequence alignment of chicken smooth muscle myosin and Drosophila MHC in the regions encoded by alternative exon 9 of the Drosophila Mhc gene. The red arrow indicates the amino acid in BH exon 9 involved in stabilizing the IHM, and the green arrow indicates the amino acid in FH exon 9 involved in stabilizing the IHM. (B) Interactions between the FH relay and BH loop 4. (C) Interaction between the BH relay and segment 2. The color coding is consistent with Figure 3.

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  Figure 7. Amino acid sequence and interaction analyses of the exon 11 encoding region. (A) Amino acid sequence alignment of chicken smooth muscle myosin and Drosophila MHC in the regions encoded by alternative exon 11 of the Drosophila Mhc gene. The red arrows indicate the amino acids in BH exon 11 involved in stabilizing the IHM, the green arrows indicate the amino acids in FH exon 11 involved in stabilizing the IHM. (B) Interactions between the FH converter, the BH loop 4 and ATP-lip. (C) Interactions between the BH converter and segment 2. The color coding is consistent with Figure 3.