Difference Between Linear and Rotary Molecular Motors

The key difference between linear and rotary molecular motors is mainly on the basis of the movement of the complexes that form the motor protein. While linear molecular motors show unidirectional linear motion among complexes, rotary molecular motors show rotatory movements around different complexes forming the molecular motor.

Molecular motors are important biomolecules that take part in many reactions, especially associated with energy generation in terms of adenosine triphosphate (ATP). They play a pivotal role in the movement or mechanical work. Motor proteins use free energy from ATP or nucleotide triphosphate hydrolysis in order to produce a mechanical force. There are two types of molecular motors as linear molecular motors and rotary molecular motors. They represent two modes of motor operation.

1. Overview and Key Difference
2. What are Linear Molecular Motors
3. What are Rotary Molecular Motors
4. Similarities Between Linear and Rotary Molecular Motors
5. Side by Side Comparison – Linear vs Rotary Molecular Motors in Tabular Form
6. Summary

What are Linear Molecular Motors?

Linear molecular motors play an important role in the movement and mechanical work of the body. They are also called cytoskeletal motor proteins. Linear molecular motors move in a unidirectional manner along the protein complexes that form the molecular motor. These linear molecular motors have the ability to use chemical energy in the form of ATP hydrolysis, which allows them to move in a linear track. There is a coupling reaction that usually takes place with a linear molecular motor in terms of ATP hydrolysis and motion.

Key Difference - Linear vs Rotary Molecular Motors

Figure 01: Actin and Myosin Molecules

There are two main linear molecular motors. They are actin motors and microtubule motors. The actin motors include myosins while the microtubule motors include the kinesins and dyneins. Myosins belong to a superfamily of actin motor proteins. They are involved in converting chemical energy to mechanical energy, thus generating force and movement. Kinesins are a type of microtubule motors that mainly take part in spindle formation during mitosis and meiosis. They are vital to spindle formation in mitotic and meiotic chromosome separation during cell. In contrast, dyneins are much complex motor molecules that participate in intracellular transport mechanisms.

What are Rotary Molecular Motors?

Rotary molecular motors mainly take part in the energy generation via ATP synthase complex and facilitate the rotatory motion between the components of the complex. The classic example of a rotary molecular motor represents the F₀–F₁ ATP synthase family of proteins. The generation of ATP is based on the proton gradient that exists across the membrane. This catalyzes the rotation of the individual subunits of the motor molecule complex that results in ATP generation.

Difference Between Linear and Rotary Molecular Motors

Figure 02: F0 – F1 ATP Synthase

Furthermore, rotary molecule motors are also present in the bacterial flagellum structure. It forms the base plate and manages the bacterial flagellar movement through the rotary molecular motor.

What are the Similarities Between Linear and Rotary Molecular Motors?

Linear and rotary motors are two types of molecular motors.
These molecular motors are present in both eukaryotic and prokaryotic cells.
Both are forms of protein subunits forming complexes known as motors.
In both types of motors, the coupling of the subunits plays an important role in its function.
They are active molecules.
Both utilize energy in the form of ATP hydrolysis or proton motive force.
They facilitate active movement.
Both are important in biochemical pathways of the cells.
Moreover, they are important in transport mechanisms.

What is the Difference Between Linear and Rotary Molecular Motors?

The key difference between linear and rotary molecular motors is the type of movement they show. While linear molecular motors facilitate unidirectional linear movement following ATP hydrolysis, rotary molecular motors facilitate rotational motion following ATP hydrolysis. Actin molecular motors and microtubule molecule motors are two examples of linear molecular motors while ATP synthase motors and flagellar motor proteins are rotary molecular motors.

The below infographic summarizes the difference between linear and molecular motors.

Summary – Linear vs Rotary Molecular Motors

Molecular motors play an important role in mediating biochemical pathways in both prokaryotes and eukaryotes. There are two main types of molecular motors as linear molecular motors and rotary molecular motors. As its name implies, linear molecular motors facilitate linear movement in between the individual subunits of the complex motor protein, which results in linear unidirectional motion. As opposed to this method of molecular motors, rotary motors enable the rotational motion of the subunits, forming the motor protein complex. The difference in movement thus attained by these two types of motors facilitates various functions in both prokaryotes and eukaryotes. So, this is the summary of the difference between linear and rotary molecular motors.

Reference:

1.Alberts, Bruce. “Molecular Motors.” Molecular Biology of the Cell. 4th Edition., U.S. National Library of Medicine, 1 Jan. 1970, Available here.
2. Erbas-Cakmak, Sundus, et al. “Rotary and Linear Molecular Motors Driven by Pulses of a Chemical Fuel.” Science, American Association for the Advancement of Science, 20 Oct. 2017, Available here.