Chains, domains, and ligands of myosin (PDB ID 1B7T): Myosin has three different chains, each with a different function. The myosin heavy chain is shown in blue, the regulatory light chain is shown in yellow, and the essential light chain is shown in green. The ligands shown here are two magnesium ions and an ADP molecule. The myosin head region has several subdomains. The upper 50 kDa subdomain is shown in green, the lower 50 kDa subdomain is shown in orange, the N-terminal subdomain is shown in cyan, the converter is shown in red, and the lever arm is shown in blue. The actin binding cleft can be seen in the first zoom and is found between the two 50 kDa subdomains. The nucleotide binding site can be seen in the second zoom and is found between the N-terminal subdomain and the upper 50 kDa subdomain. ADP is shown in CPK colors.

Active Site of Scallop Myosin (PDB ID 1B7T): Shown here is the site at which ATP binds and its hydrolysis to ADP and a phosphate ion occurs. The active site is composed of several key components. Arg-128 is essential in binding of the nucleotide. When nucleotide is not bound, it swings into the solvent to allow binding. When ATP/ADP is bound, as it is here (shown in green), it swings into the protein to form a salt bridge with Glu-184. These two residues are shown in CPK colors. The purine binding loop is shown in cyan and allows exclusive purine binding. The most important residue to purine binding is thought to be Arg-127, shown in ball and stick conformation in cyan. Switch I and the P-loop are important to holding the gamma phosphorous and are shown in orange and yellow, respectively.

Catalytic Mechanism Found in Dictyostelium discoideum Myosin (PDB ID 1VOM) This button shows the hypothesized conformation of the active site at the time of ATP hydrolysis. The hypothesis states that at the time of the formation of the salt bridge between Arg-238 and Glu-459, seen here, two waters are also bound and oriented in a way that allows nucleophilic attack at the gamma phosphorous by the -OH group on water. The other water acts as a proton acceptor. In this crystal structure, the ligand shown in yellow is ADP. In green, the gamma phosphate analog vanadate is shown. Water one is not seen in the file, but it has been hypothesized that the oxygen atom in vanadate takes its place. This oxygen atom changes color from green to red. Water two, the potential proton acceptor, is seen in cyan. The salt bridge is shown in CPK colors.

Powerpoint Presentation This is the animation for the oral report