Event Title

Arachidonic Acid and Oxidation in the Myosin II Motor Domain

Presenter Information

Kellie Wong, Minnesota State University, Mankato

Location

CSU Ballroom

Start Date

10-4-2018 10:00 AM

End Date

10-4-2018 11:30 AM

Student's Major

Chemistry and Geology

Student's College

Science, Engineering and Technology

Mentor's Name

Rebecca Moen

Mentor's Department

Chemistry and Geology

Mentor's College

Science, Engineering and Technology

Description

Myosin is the motor protein responsible for movement and muscle contraction in all eukaryotic cells. The catalytic motor domain of myosin II contains three functionally important subdomains: the actin-binding cleft, the force-generating domain, and the nucleotide binding pocket. The chemomechanical coupling in the myosin catalytic domain allows for hydrolysis of adenosine triphosphate (ATP) into adenosine diphosphate (ADP) and inorganic phosphate (Pi), producing the energy needed for the contraction of muscle. This chemical reaction of ATP hydrolysis in the nucleotide binding cleft must be accompanied by a crucial interaction with actin to allow for the proper production of mechanical force. Various physiological and pharmacological effector molecules interact with myosin specifically in its actin-binding cleft and affect the actomyosin functional interaction. For example, oxidation of a methionine amino acid residue in the actin-binding cleft, M394, decreases myosin's actin-activated ATPase activity and changes the structural dynamics of the actin-binding cleft of myosin (1). Conversely, arachidonic acid, a bioactive lipid produced naturally in eukaryotic cells, acts as a positive allosteric effector of myosin and is postulated to bind near the actin-binding cleft of myosin, increasing the rate at which myosin hydrolyzes ATP (2). We have investigated the combined functional and structural effects of oxidation and arachidonic acid on the myosin motor domain in a Dictyostelium myosin II model system. Changes in actomyosin functional interaction in the presence of arachidonic acid after in vitro oxidation was assessed using a myosin ATPase activity assay and an actomyosin cosedimentation assay while changes in structural dynamics of the actin-binding cleft was investigated using electron paramagnetic resonance (EPR). The results illustrate the importance of myosin's actin-binding cleft structural dynamics and how allosteric effectors effect actomyosin functional interaction.