AI Article Synopsis
- Myosin's motor and enzymatic activities are controlled by a regulatory domain (RD) on its lever arm, toggling between on and off states.
- The on-state is activated through phosphorylation of the regulatory light chain (RLC) or by calcium binding to the essential light chain (ELC), while crystal structures have only been characterized for the molluscan RD.
- The recent study revealed that the absence of calcium disrupts interactions between the light chains, increasing the RD's flexibility and suggesting that the loss of key links with the RLC initiates the off-state in smooth muscle and molluscan myosins.
Article Abstract
In regulated myosin, motor and enzymatic activities are toggled between the on-state and off-state by a switch located on its lever arm domain, here called the regulatory domain (RD). This region consists of a long alpha-helical "heavy chain" stabilized by a "regulatory" light chain (RLC) and an "essential" light chain (ELC). The on-state is activated by phosphorylation of the RLC of vertebrate smooth muscle RD or by direct binding of Ca(2+) to the ELC of molluscan RD. Crystal structures are available only for the molluscan RD. To understand in more detail the pathway between the on-state and the off-state, we have now also determined the crystal structure of a molluscan (scallop) RD in the absence of Ca(2+). Our results indicate that loss of Ca(2+) abolishes most of the interactions between the light chains and may increase the flexibility of the RD heavy chain. We propose that disruption of critical links with the C-lobe of the RLC is the key event initiating the off-state in both smooth muscle myosins and molluscan myosins.
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| http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2997636 | PMC |
| http://dx.doi.org/10.1016/j.jmb.2009.09.035 | DOI Listing |
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