P-loop
Encyclopedia : P : PL : PLO : P-loop
A P-loop or phosphate-binding loop, is an ATP/GTP binding site motif found in many nucleotide-binding proteins. It is a flexible loop between the first β-strand and the first α-helix of the protein and can interact with one of the phosphate groups of the nucleotide. Typically it has the amino acid sequence Ala/Gly-X-X-X-X-Gly-Lys-Ser/Thr. Nucleotide-binding proteins share several more or less conserved sequence motifs, the P-loop is the best conserved one of these. It is widelyspread, probably because of its ability to help the protein to undergo great conformational changes on nucleotide binding and hydrolysis.
Some proteins bind nucleotides in a completely different way and has no p-loop, examples include glycolytic kinases and E1-E2 ATPases.
Some proteins with P-loops include ATP synthase, myosin, transducin, helicase and G-proteins.
References
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