Walker motifs

The Walker A and Walker B motifs are protein sequence motifs, known to have highly conserved three-dimensional structures. These were first reported in ATP-binding proteins by Walker and co-workers in 1982.

Of the two motifs, the A motif is the main "P-loop" responsible for binding phosphate, while the B motif is a much less conserved downstream region. The P-loop is best known for its presence in ATP- and GTP-binding proteins, and is also found in a variety of proteins with phosphorylated substrates. Major lineages include:

• RecA and rotor ATP synthase / ATPases (α and β subunits).
• Nucleic acid-dependent ATPases: helicases, Swi2, and PhoH (InterPro: IPR003714)
• AAA proteins
• STAND NTPases including MJ, PH, AP, and NACHT ATPases
• ABC-PilT ATPases
• Nucleotide kinases (InterPro: IPR000850)
• G domain proteins: G-proteins (transducin), myosin.