Myosinemotoren

Myosinemotoren, or myosin motors, are a large family of ATP-dependent motor proteins that convert chemical energy from ATP into mechanical work, allowing movement along actin filaments. They are essential for muscle contraction and for a wide range of intracellular transport, organization, and signaling tasks. The term encompasses multiple classes found in many eukaryotes, including muscle and non-muscle myosins.

Each myosin molecule typically contains a head or motor domain that binds actin and ATP, a neck region with light chains acting as a lever arm, and a tail that determines cargo binding or filament association. In the chemomechanical cycle, ATP binding causes detachment from actin, ATP hydrolysis primes the motor, and release of phosphate triggers a power stroke that moves the head along actin. After ADP release, a new ATP molecule binds and the cycle restarts.

Most myosins move toward the plus end of actin filaments, but some classes translocate toward the opposite minus end; for example, myosin VI is known to move toward the minus end. In muscle, myosin II forms thick filaments that interact with actin to drive contraction, while non-muscle myosins participate in cargo transport, endocytosis, organelle positioning, and cell migration.

There is substantial diversity—dozens of myosin genes encode at least 35 distinct classes with specialized tissue distributions and functions. Regulation occurs through phosphorylation of regulatory light chains, adaptor proteins, and, in muscle, the troponin–tropomyosin system that controls access of myosin heads to actin.

Mutations in myosin genes underlie several human diseases, notably cardiomyopathies and some congenital myopathies. Beyond physiology, myosin motors are a focus of structural and biophysical studies using crystallography and cryo-electron microscopy to reveal their catalytic cycles and mechanisms of force production.