ATP-binding motif

The short motifs involving ATP-binding are the Walker motifs, Walker A, also known as the P-loop, and Walker B, as well as the C motif and switch motif. Walker A motif The Walker site A has a primary amino acid sequence of or . The letter can represent any amino acid. Walker B motif The primary amino acid sequence of the Walker B site is , in which represents any hydrophobic amino acid. Due to the variety of different amino acids that can be used in the primary sequence, of both the Walker site A and B, the non-variant amino acids within the sequence are highly conserved. A mutation of any of these amino acids will affect the binding ATP or interfere with the catalytic activity of the enzyme. The primary amino acid sequence determines the three dimensional structure of each motif. == Structure ==

All of the ATP binding domains are made up of an estimated 250 residues and two subunits, creating a dimer. These residues are folded into six α-helices and five β-strands. Walker A motif Structurally, the Walker A motif consists of an α-helix and is always followed by a glycine-rich loop. Walker B motif The Walker B motif is a β-strand. The Walker motifs are connected to each other by a peptide sequence of about 100 residues. Structurally, these connecting residues fold into an α-helical domain. C motif Directly following the Walker B motif, is the signature motif. Switch motif The switch motif has been found to be located at the end of the β4-strand in ATP-binding proteins. == Function ==

Each ATP binding motif has a different role to play whether it is directly involved with the binding of ATP or helping with the construction of the ATP-binding cassette (ABC) transporter. ==References==