Motor proteins are non-enzymatic proteins that perform mechanical movement in cells or muscles.

Motor proteins use adenosine triphosphate (ATP) hydrolysis to generate energy to allow for a conformational change in their shape causing movement with the biomolecules it is bound too.

In muscle contraction, myosin filaments bind to actin filaments in the muscle and as myosin releases a phosphate molecule it changes shape moving the actin filament with it. The myosin filament then returns to its resting position using the hydrolysis of ATP.

Two other examples of motor proteins are kinesin and dynein. Kinesins move along microtubule filaments in an anterograde direction (center to periphery) to transport cargo within the cell. Dyneins move along microtubule filaments in a retrograde direction to transport various cellular cargos. They can also convert the chemical energy stored in ATP to provide movement in mitosis as well as the movement of flagella and cilia in single cell organisms.

Practice Questions

Khan Academy

MCAT Official Prep (AAMC)

Online Flashcards Biology Question 12

Sample Test B/B Section Passage 1 Question 4

Key Points

• Myosin is a non-enzymatic protein that is involved in muscle movement

• Kinesin is a motor protein that moves along microtubule filaments in an anterograde direction (center to periphery) to transport cargo within the cell.

• Dynein is a motor protein that moves along microtubule filaments in a retrograde direction to transport various cellular cargos.

Key Terms

Myosin: a motor protein that forms myofilaments that interact with actin filaments to generate tension.

Actin: a protein that forms myofilaments that interact with myosin filaments to generate tension.

Kinesin: a protein belonging to a class of motor proteins found in eukaryotic cells

Hydrolysis: a reaction in which breakdown of the molecule occurs due to reaction with water

Adenosine triphosphate (ATP):  an energy-carrying molecule found in the cells of all living things

Dynein: a family of cytoskeletal motor proteins that move along microtubules in cells

Anterograde: occurring or performed in the normal or forward direction of conduction or flow (center to periphery)

Retrograde: having a direction opposed to the normal or usual (periphery to center)