3j04

EM structure of the heavy meromyosin subfragment of Chick smooth muscle Myosin with regulatory light chain in phosphorylated stateEM structure of the heavy meromyosin subfragment of Chick smooth muscle Myosin with regulatory light chain in phosphorylated state

3j04, resolution 20.00Å Show:Asymmetric Unit Biological Assembly Structural highlights 3j04 is a 6 chain structure with sequence from Chick. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Experimental data: Check Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function [MYH11_CHICK] Muscle contraction. [MYL6_CHICK] Regulatory light chain of myosin. Does not bind calcium. [MLRM_CHICK] Myosin regulatory subunit that plays an important role in regulation of both smooth muscle and nonmuscle cell contractile activity. Implicated in cytokinesis, receptor capping, and cell locomotion (By similarity). Publication Abstract from PubMed Smooth muscle myosin and smooth muscle heavy meromyosin (smHMM) are activated by regulatory light chain phosphorylation, but the mechanism remains unclear. Dephosphorylated, inactive smHMM assumes a closed conformation with asymmetric intramolecular head-head interactions between motor domains. The "free head" can bind to actin, but the actin binding interface of the "blocked head" is involved in interactions with the free head. We report here a three-dimensional structure for phosphorylated, active smHMM obtained using electron crystallography of two-dimensional arrays. Head-head interactions of phosphorylated smHMM resemble those found in the dephosphorylated state but occur between different molecules, not within the same molecule. The light chain binding domain structure of phosphorylated smHMM differs markedly from that of the "blocked" head of dephosphorylated smHMM. We hypothesize that regulatory light chain phosphorylation opens the inhibited conformation primarily by its effect on the blocked head. Singly phosphorylated smHMM is not compatible with the closed conformation if the blocked head is phosphorylated. This concept has implications for the extent of myosin activation at low levels of phosphorylation in smooth muscle. Phosphorylated Smooth Muscle Heavy Meromyosin Shows an Open Conformation Linked to Activation.,Baumann BA, Taylor DW, Huang Z, Tama F, Fagnant PM, Trybus KM, Taylor KA J Mol Biol. 2011 Nov 4. PMID:22079364 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See Also Myosin 3D Structures