Abstract
The P-loop NTPases are involved in diverse cellular functions. Members of the P-loop NTPase superfamily are characterized by presence of a highly conserved sequence pattern GxxxxGKS/T, known as Walker A motif. This motif adopts an archetypal P-loop conformation which allows accommodation of the triphosphate moiety of a bound nucleotide. Despite the presence of Walker A as a common sequence motif, P-loop NTPases exhibit extreme sequence divergence which hampers their phylogenetic or evolutionary classification. Here, we show that P-loop and its flanking region subsequence (termed as "extended-WalkerA motif") contain distinct signatures that can be utilized to classify NTPase domain of functionally diverse proteins. We find a clearly classified group of diverse NTPases of Conserved Domain Database such as G-proteins, Ylqf, RecA like, DExDc, AAA, CPT, NK, ABC transporter and NifH proteins.