P-loop containing Nucleoside Triphosphate Hydrolases; Members of the P-loop NTPase domain superfamily are characterized by a conserved nucleotide phosphate-binding motif, also referred to as the Walker A motif (GxxxxGK[S/T], where x is any residue), and the Walker B motif (hhhh[D/E], where h is a hydrophobic residue). The Walker A and B motifs bind the beta-gamma phosphate moiety of the bound nucleotide (typically ATP or GTP) and the Mg2+ cation, respectively. The P-loop NTPases are involved in diverse cellular functions, and they can be divided into two major structural classes: the KG (kinase-GTPase) class which includes Ras-like GTPases and its circularly permutated YlqF-like; and the ASCE (additional strand catalytic E) class which includes ATPase Binding Cassette (ABC), DExD/H-like helicases, 4Fe-4S iron sulfur cluster binding proteins of NifH family, RecA-like F1-ATPases, and ATPases Associated with a wide variety of Activities (AAA). Also included are a diverse set of nucleotide/nucleoside kinase families.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1958676286 618 LVVLSALGVPGTGKSTLLNTMFGLK--FATGRSCS--ARGAFMQLLPVAEGFSQDLGcdqILVIDSGGLiSGALASAGDR 693
Cdd:cd01851     7 VVVVSVFGSQSSGKSFLLNHLFGTSdgFDVMDTSQqtTKGIWMWSDPFKDTDGKKHA---VLLLDTEGT-DGRERGEFEN 82

                          90       100
                  ....*....|....*....|....*
gi 1958676286 694 FELEASLATLlmgLSNVTVVSLAET 718
Cdd:cd01851    83 DARLFALATL---LSSVLIYNMWQT 104

Guanylate-binding protein (GBP) family (N-terminal domain); Guanylate-binding protein (GBP), N-terminal domain. Guanylate-binding proteins (GBPs) define a group of proteins that are synthesized after activation of the cell by interferons. The biochemical properties of GBPs are clearly different from those of Ras-like and heterotrimeric GTP-binding proteins. They bind guanine nucleotides with low affinity (micromolar range), are stable in their absence and have a high turnover GTPase. In addition to binding GDP/GTP, they have the unique ability to bind GMP with equal affinity and hydrolyze GTP not only to GDP, but also to GMP. Furthermore, two unique regions around the base and the phosphate-binding areas, the guanine and the phosphate caps, respectively, give the nucleotide-binding site a unique appearance not found in the canonical GTP-binding proteins. The phosphate cap, which constitutes the region analogous to switch I, completely shields the phosphate-binding site from solvent such that a potential GTPase-activating protein (GAP) cannot approach.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1958676286 618 LVVLSALGVPGTGKSTLLNTMFGLK--FATGRSCS--ARGAFMQLLPVAEGFSQDLGcdqILVIDSGGLiSGALASAGDR 693
Cdd:cd01851     7 VVVVSVFGSQSSGKSFLLNHLFGTSdgFDVMDTSQqtTKGIWMWSDPFKDTDGKKHA---VLLLDTEGT-DGRERGEFEN 82

                          90       100
                  ....*....|....*....|....*
gi 1958676286 694 FELEASLATLlmgLSNVTVVSLAET 718
Cdd:cd01851    83 DARLFALATL---LSSVLIYNMWQT 104

Guanylate-binding protein (GBP) family (N-terminal domain); Guanylate-binding protein (GBP), N-terminal domain. Guanylate-binding proteins (GBPs) define a group of proteins that are synthesized after activation of the cell by interferons. The biochemical properties of GBPs are clearly different from those of Ras-like and heterotrimeric GTP-binding proteins. They bind guanine nucleotides with low affinity (micromolar range), are stable in their absence and have a high turnover GTPase. In addition to binding GDP/GTP, they have the unique ability to bind GMP with equal affinity and hydrolyze GTP not only to GDP, but also to GMP. Furthermore, two unique regions around the base and the phosphate-binding areas, the guanine and the phosphate caps, respectively, give the nucleotide-binding site a unique appearance not found in the canonical GTP-binding proteins. The phosphate cap, which constitutes the region analogous to switch I, completely shields the phosphate-binding site from solvent such that a potential GTPase-activating protein (GAP) cannot approach.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1958676286 618 LVVLSALGVPGTGKSTLLNTMFGLK--FATGRSCS--ARGAFMQLLPVAEGFSQDLGcdqILVIDSGGLiSGALASAGDR 693
Cdd:cd01851     7 VVVVSVFGSQSSGKSFLLNHLFGTSdgFDVMDTSQqtTKGIWMWSDPFKDTDGKKHA---VLLLDTEGT-DGRERGEFEN 82

                          90       100
                  ....*....|....*....|....*
gi 1958676286 694 FELEASLATLlmgLSNVTVVSLAET 718
Cdd:cd01851    83 DARLFALATL---LSSVLIYNMWQT 104