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29.3 CFTR protein:

• •  CFTR protein is a chloride ion channel involved in creating sweat, digestive juices and mucus.

•  It is a 1480 amino acid membrane bound glycoprotein with a molecular mass of 170kDa.

•  It belongs to the ABC superfamily of proteins.

•  It comprises of a pair of six span membrane bound regions each connected to a nuclear binding factor (NBF) which binds ATP.

•  An R-domain is present between these two units which comprises of numerous charged amino acids. Within the ABC superfamily the R-domain is the main characteristic of CFTR protein and has protein kinase A (PKA) and protein kinase C activity.

•  This channel opens only when the R domain gets phosphorylated by PKA and ATP is bound to the nuclear binding domain (NBD).

Figure 29.1 Schematic representation of a CFTR protein: