Factor IX: Difference between revisions
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In the presence of [[calcium ions the Gla domain]] (Calcium ions 5 and 6 and Gla residues 17 and 21) interacts with serine head group of phosphatidylserine located on the phospholipid membrane (2). In the absence of metal ions the Gla domain is highly disordered and unstructured which indicated that the metal ions, stabilize the structure (4-6). Three Mg2+ ions, (Mg-1, Mg-7, and Mg-8) are located on the surface of FIX and correspond to FX, three Ca2+ ions (Ca-1, Ca-7, and Ca-8). Each Mg2+ ion has a bipyramidal coordination with a water molecule (Mg–O in FIX is 2.12 Å, whereas the Ca–O distances in FX is 2.41 Å) and a pair of Gla residues. | In the presence of [[calcium ions the Gla domain]] (Calcium ions 5 and 6 and Gla residues 17 and 21) interacts with serine head group of phosphatidylserine located on the phospholipid membrane (2). In the absence of metal ions the Gla domain is highly disordered and unstructured which indicated that the metal ions, stabilize the structure (4-6). Three Mg2+ ions, (Mg-1, Mg-7, and Mg-8) are located on the surface of FIX and correspond to FX, three Ca2+ ions (Ca-1, Ca-7, and Ca-8). Each Mg2+ ion has a bipyramidal coordination with a water molecule (Mg–O in FIX is 2.12 Å, whereas the Ca–O distances in FX is 2.41 Å) and a pair of Gla residues. | ||
To identify the exact locations of bound Mg2+ ions, crystal structures comparisons were made between Mg2+-free and Mg2+-bound conditions. In the Mg2+-free conditions, Mg-1, Mg-7, and Mg-8, were replaced by Ca2+ ions which induced an elongation of the bond between the ion and an oxygen atom from a distance of 2.11 to 2.34 Å. This small change in distance induces a rotation of 4 degrees of FIX | To identify the exact locations of bound Mg2+ ions, crystal structures comparisons were made between Mg2+-free and Mg2+-bound conditions. In the Mg2+-free conditions, Mg-1, Mg-7, and Mg-8, were replaced by Ca2+ ions which induced an elongation of the bond between the ion and an oxygen atom from a distance of 2.11 to 2.34 Å. This small change in distance induces a [[rotation of 4 degrees of FIX]]. This suggests that the magnisuim ions induce a closed form conformation that contributes to the tight association of the Gla domain. This situation probably arises mainly from a difference in length between O–Mg–O and O–Ca–O bridges. | ||
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