G1Ploop

G1Ploop is a descriptive label used in molecular biology to denote a subset of P-loop nucleoside triphosphatases (NTPases) defined by the presence of the G1 motif within the phosphate-binding loop. The term emphasizes the conserved G1 motif, the first in the canonical G1–G5 sequence motifs found in many P-loop NTPases, and is employed to group diverse proteins that share this common feature.

Structurally, G1Ploop proteins typically contain the Walker A motif, also known as the G1 motif, with a consensus sequence such as GxxxxGKT/S, which coordinates nucleotide phosphate groups. This is usually accompanied by the Walker B motif and other structural elements that form a catalytic core. Many G1Ploop proteins also feature additional loops or domains that regulate activity, substrate specificity, or interactions with effectors, enabling a range of regulatory mechanisms.

Functionally, G1Ploop proteins act as molecular switches that cycle between active and inactive states through hydrolysis of ATP or GTP. The nucleotide-bound state drives conformational changes that control interactions with partner proteins, membranes, or nucleic acids. Because of their versatility, G1Ploop members participate in diverse cellular processes, including signal transduction, vesicle trafficking, cytoskeleton dynamics, and DNA metabolism, with specific roles varying across organisms and family members.

Distribution and evolution-wise, the G1Ploop label encompasses a broad superfamily rather than a single gene family. Members are found across bacteria, archaea, and eukaryotes, and have diversified through domain fusions, insertions, and lineage-specific adaptations. Nomenclature can vary, and some databases may classify G1Ploop proteins alongside related P-loop NTPases, Ras-like GTPases, or the SIMIBI class, leading to occasional annotation differences.

See also: P-loop NTPase, Walker A motif, GTPase, Ras-like GTPase.