Part IV: Open Sesame Among the numerous ion channels in cell membranes, there ar
ID: 132473 • Letter: P
Question
Part IV: Open Sesame Among the numerous ion channels in cell membranes, there are two principal types: voltagegated and ligandgated. Voltagegated channels are triggered to open and shut their doors by changes in the electric potential difference across the membrane. Ligandgated channels, in contrast, require a special "key" to unlock their doors, which usually comes in the form of a small molecule CFTR is a ligandgated channel, but it's an unusual one. Its "key" is ATP, a small molecule that plays a critical role in the storage and release of energy within cells in the body. CFTR has two nucleotide binding domains, which bind to ATP. In order to open the gate, CFTR channel must first snip a phosphate group- one of three "P's" - off the ATP molecule. The extra phosphates then bind to the regulatory domain, somehow displacing it from blocking the channel and allowing Cl- to pass. 12. Channels that require ATP binding and dephosphorylation to translocate substances across the cell membrane are called active transporters or pumps. What is different between most of these transporters and the CFTR?Explanation / Answer
Cystic fibrosis transmembrane conductance regulator (CFTR) is an ATP gated anion-channel. it is remarkably different from other transportors in two ways.
1. CFTR is considered as the only ATP-binding cassette (ABC) transporter which is known to be an ion channel. But others functions as transport ATPase. This is the only ABC transporter act as a chloride pore, instead of actively transporting substances. so it has a unique property of pore formation than other transportors.
2. CFTR is the only ligand -gated channel, which consumes its ligand i.e. ATP, during the gating process( ABC Transporting process).