Cystic fibrosis is a genetic disease in humans in which the CFTR protein, which functions as a chloride ion channel, is missing or nonfunctional in cell membranes. The CFTR protein belongs to what category of membrane proteins

ABC transporter protein

Explanation:

ABC transporter protein refers to the ATP binding cassette protein which utilizes the AT energy to transport the substrates from one side to another side. The ABC proteins are one of the oldest proteins known in the organisms.

The CFTR protein which acts as a chloride channel in the membrane which transports the chloride ions across the membrane utilizes the ATP energy in the transport.

Thus, ABC transporter protein is correct