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.

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                 ....*....|....*....|....*....|....*....|..
gi 359828342   1 MVDVGGLRSERRKWIHCFENVTSIMFLVALSEYDQVLVESDN 42
Cdd:cd00066  165 MFDVGGQRSERKKWIHCFEDVTAIIFVVALSEYDQVLVEDES 206

Alpha subunit of G proteins (guanine nucleotide binding); The alpha subunit of G proteins contains the guanine nucleotide binding site. The heterotrimeric GNP-binding proteins are signal transducers that communicate signals from many hormones, neurotransmitters, chemokines, and autocrine and paracrine factors. Extracellular signals are received by receptors, which activate the G proteins, which in turn route the signals to several distinct intracellular signaling pathways. The alpha subunit of G proteins is a weak GTPase. In the resting state, heterotrimeric G proteins are associated at the cytosolic face of the plasma membrane and the alpha subunit binds to GDP. Upon activation by a receptor GDP is replaced with GTP, and the G-alpha/GTP complex dissociates from the beta and gamma subunits. This results in activation of downstream signaling pathways, such as cAMP synthesis by adenylyl cyclase, which is terminated when GTP is hydrolized and the heterotrimers reconstitute.

                         10        20        30        40
                 ....*....|....*....|....*....|....*....|..
gi 359828342   1 MVDVGGLRSERRKWIHCFENVTSIMFLVALSEYDQVLVESDN 42
Cdd:cd00066  165 MFDVGGQRSERKKWIHCFEDVTAIIFVVALSEYDQVLVEDES 206

G-protein alpha subunit; G proteins couple receptors of extracellular signals to intracellular signaling pathways. The G protein alpha subunit binds guanyl nucleotide and is a weak GTPase. A set of residues that are unique to G-alpha as compared to its ancestor the Arf-like family form a ring of residues centered on the nucleotide binding site. A Ggamma is found fused to an inactive Galpha in the Dictyostelium protein gbqA.

                          10        20        30        40
                  ....*....|....*....|....*....|....*....|..
gi 359828342    1 MVDVGGLRSERRKWIHCFENVTSIMFLVALSEYDQVLVESDN 42
Cdd:pfam00503 171 LFDVGGQRSERKKWIHCFEDVTAIIFVVSLSEYDQVLYEDDS 212

Alpha subunit of G proteins (guanine nucleotide binding); The alpha subunit of G proteins contains the guanine nucleotide binding site. The heterotrimeric GNP-binding proteins are signal transducers that communicate signals from many hormones, neurotransmitters, chemokines, and autocrine and paracrine factors. Extracellular signals are received by receptors, which activate the G proteins, which in turn route the signals to several distinct intracellular signaling pathways. The alpha subunit of G proteins is a weak GTPase. In the resting state, heterotrimeric G proteins are associated at the cytosolic face of the plasma membrane and the alpha subunit binds to GDP. Upon activation by a receptor GDP is replaced with GTP, and the G-alpha/GTP complex dissociates from the beta and gamma subunits. This results in activation of downstream signaling pathways, such as cAMP synthesis by adenylyl cyclase, which is terminated when GTP is hydrolized and the heterotrimers reconstitute.

                         10        20        30        40
                 ....*....|....*....|....*....|....*....|..
gi 359828342   1 MVDVGGLRSERRKWIHCFENVTSIMFLVALSEYDQVLVESDN 42
Cdd:cd00066  165 MFDVGGQRSERKKWIHCFEDVTAIIFVVALSEYDQVLVEDES 206

G-protein alpha subunit; G proteins couple receptors of extracellular signals to intracellular signaling pathways. The G protein alpha subunit binds guanyl nucleotide and is a weak GTPase. A set of residues that are unique to G-alpha as compared to its ancestor the Arf-like family form a ring of residues centered on the nucleotide binding site. A Ggamma is found fused to an inactive Galpha in the Dictyostelium protein gbqA.

                          10        20        30        40
                  ....*....|....*....|....*....|....*....|..
gi 359828342    1 MVDVGGLRSERRKWIHCFENVTSIMFLVALSEYDQVLVESDN 42
Cdd:pfam00503 171 LFDVGGQRSERKKWIHCFEDVTAIIFVVSLSEYDQVLYEDDS 212