1sr6
From Proteopedia
Structure of nucleotide-free scallop myosin S1
Structural highlights
Function[MYS_ARGIR] Muscle contraction. Myosin is a protein that binds to F-actin and has ATPase activity that is activated by F-actin. [MLE_ARGIR] In molluscan muscle, calcium regulation is associated with myosin rather than with actin. Muscle myosin contains two types of light chains: the catalytic light chain, essential for ATPase activity, and the regulatory light chain, a calcium-binding protein responsible for Ca(2+) dependent binding and Ca(2+) dependent Mg-ATPase activity. [MLR_ARGIR] In molluscan muscle, calcium regulation is associated with myosin rather than with actin. Muscle myosin contains two types of light chains: the catalytic light chain, essential for ATPase activity, and the regulatory light chain, a calcium-binding protein responsible for Ca(2+) dependent binding and Ca(2+) dependent Mg-ATPase activity. Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedStructural studies of myosin have indicated some of the conformational changes that occur in this protein during the contractile cycle, and we have now observed a conformational change in a bound nucleotide as well. The 3.1-A x-ray structure of the scallop myosin head domain (subfragment 1) in the ADP-bound near-rigor state (lever arm =45 degrees to the helical actin axis) shows the diphosphate moiety positioned on the surface of the nucleotide-binding pocket, rather than deep within it as had been observed previously. This conformation strongly suggests a specific mode of entry and exit of the nucleotide from the nucleotide-binding pocket through the so-called "front door." In addition, using a variety of scallop structures, including a relatively high-resolution 2.75-A nucleotide-free near-rigor structure, we have identified a conserved complex salt bridge connecting the 50-kDa upper and N-terminal subdomains. This salt bridge is present only in crystal structures of muscle myosin isoforms that exhibit a strong reciprocal relationship (also known as coupling) between actin and nucleotide affinity. Myosin subfragment 1 structures reveal a partially bound nucleotide and a complex salt bridge that helps couple nucleotide and actin binding.,Risal D, Gourinath S, Himmel DM, Szent-Gyorgyi AG, Cohen C Proc Natl Acad Sci U S A. 2004 Jun 15;101(24):8930-5. Epub 2004 Jun 7. PMID:15184651[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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