Question

CELL BIOLOGY
Consider three types of molecular motor proteins: kinesin 1, cytoplasmic dynein, myosin II. First, make a list of several properties and functions that these proteins have in common, and then second, make a list of ways that these proteins differ from each other. When considered together, your lists should provide a summary of the roles of these proteins in cellular motility.

Answer 1

A class of molecular motors that helps in the conversion of the chemical energy into mechanical energy and work with the ATP hydrolysis and can move and travel along the animal cell's cytoplasm is known as motor proteins. The best pre-eminent example of a motor protein is the myosin muscle protein that helps in the muscle fibers contraction in animals.

The driving force behind the most active transport of vesicles and proteins present in the cytoplasm is the motor proteins. The cytoplasmic dyneins and kinesins play a crucial role in intracellular transport like axonal transport and the spindle apparatus formation and the separation of the chromosomes during meiosis and mitosis. The axonemal dynein present in flagella and cilia is important for cell motility.

The similarities and common features between kinesin 1, cytoplasmic dynein, and myosin II are:

• All of these molecular motor proteins are ATP driven.
• They help in the transport of the molecular cargo like membrane vesicles , proteins, and organelles within cells.
• These molecular motor proteins have globular ATP-binding heads that interact with the microtubules and function as the motor domain.
• These molecular motor proteins have a tail domain that is involved in cargo binding.
• The dynein and kinesin help in keeping the cell organelles correctly positioned.

The differences between kinesin 1, cytoplasmic dynein, and myosin II are:

• The majority of the kinesins travel away from the cell center, i.e, toward the plus end of the microtubule that they are on. Therefore, kinesins bring cargoes to the periphery of the cell, whereas, dyneins carry cargoes to the cell center.
• The dynein complex are more complex and much larger than myosin and kinesin motors.
• The myosin moves and passes along actin microfilaments, while kinesin moves and passes along microtubules.