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The P-loop main chain is shown in red, the Mg 2+ ion as green sphere and the side chains of the amino acids K16 and S17 are shown as sticks. Walker A motif, also known as the Walker loop, or P-loop, or phosphate-binding loop, is a motif in proteins that is associated with phosphate binding. The motif has the pattern G-x (4)-GK- [TS], where G, K ...
The C motif, also known as the signature motif, LSGGQ motif, or the linker peptide, has a primary amino acid sequence of LSGGQQ/R/KQR. [8] [9]Due to the variety of different amino acids that can be used in the primary sequence, of both the Walker site A and B, the non-variant amino acids within the sequence are highly conserved.
Guanosine-5'-triphosphate (GTP) is a purine nucleoside triphosphate. It is one of the building blocks needed for the synthesis of RNA during the transcription process. Its structure is similar to that of the guanosine nucleoside , the only difference being that nucleotides like GTP have phosphates on their ribose sugar.
Hydrolysis of GTP bound to an (active) G domain-GTPase leads to deactivation of the signaling/timer function of the enzyme. [2] [3] The hydrolysis of the third (γ) phosphate of GTP to create guanosine diphosphate (GDP) and P i, inorganic phosphate, occurs by the S N 2 mechanism (see nucleophilic substitution) via a pentacoordinate transition state and is dependent on the presence of a ...
The water molecule attacks the γ-phosphate of GTP, leading to the formation of a pentavalent transition state. This transition state is stabilized by interactions with the active site residues, including conserved catalytic residues. As a result, the γ-phosphate is cleaved, and inorganic phosphate (Pi) is released.
The GTP form of the α subunit of transducin (G t) activates the cyclic GMP phosphodiesterase from retinal rod outer segments, [3] and the GTP form of the α subunit of the stimulatory G protein (G s) activates hormone-sensitive adenylate cyclase. [4] [5] More than one type of G protein co-exist in the same tissue. For example, in adipose ...
Small GTPases (EC 3.6.5.2), also known as small G-proteins, are a family of hydrolase enzymes that can bind and hydrolyze guanosine triphosphate (GTP). They are a type of G-protein found in the cytosol that are homologous to the alpha subunit of heterotrimeric G-proteins, but unlike the alpha subunit of G proteins, a small GTPase can function independently as a hydrolase enzyme to bind to and ...
GDP. Guanine nucleotide exchange factors (GEFs) are proteins or protein domains that activate monomeric GTPases by stimulating the release of guanosine diphosphate (GDP) to allow binding of guanosine triphosphate (GTP). [1] A variety of unrelated structural domains have been shown to exhibit guanine nucleotide exchange activity.