Sandbox 172: Difference between revisions
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[[Image:Hexlobes.jpg|thumb|right|The C-terminal and N-terminal regions of Hexokinase Type I - held together by hydrogen bonding and a connecting helix.]] | [[Image:Hexlobes.jpg|thumb|right|The C-terminal and N-terminal regions of Hexokinase Type I - held together by hydrogen bonding and a connecting helix.]] | ||
===Glucose Binding Sites=== | ===Glucose Binding Sites=== | ||
The residues of the glucose binding site of Hexokinase Type I are very highly conserved within the hexokinase sequence; glucose binds equally to both domains or "lobes" of the structure. As a result, hexokinase type I in its native conformation has an active site in its inactive regulatory domains. Before glucose binds to hexokinase type I, it is said to be in an open conformation. ATP is already bound within one of the domains but it is situated a distance from the glucose binding site. As the glucose binds, the two domains close around the glucose substrate and this change results in a newly formed pattern of hydrogen bonding. | The residues of the glucose binding site of Hexokinase Type I are very highly conserved within the hexokinase sequence; glucose binds equally to both domains or "lobes" of the structure. As a result, hexokinase type I in its native conformation has an active site in its inactive regulatory domains. Before glucose binds to hexokinase type I, it is said to be in an open conformation. ATP is already bound within one of the domains but it is situated a distance from the glucose binding site. As the glucose binds, the two domains close around the glucose substrate and this change results in a newly formed pattern of hydrogen bonding.<ref name="one" /> | ||
[[Image:Glucosebinding.jpg|thumb|left|The conformational change in hexokinase caused by glucose binding.]] | [[Image:Glucosebinding.jpg|thumb|left|The conformational change in hexokinase caused by glucose binding.]] | ||
===Active Site=== | ===Active Site=== | ||
In the <scene name='Sandbox_172/Mynewscene/2'>active site</scene> of hexokinase type I, Lys 621 and Asp 657 show the hydrogen-bonding distance in which a reactive O6 hydroxyl is situated in between. Here Lys 621 functions to aid the transfer of the phosphate moiety which is negatively charged; Asp 657 serves as a catalytic base or to position the glucose O6 correctly for phosphoryl transfer to take place. Though it may seem that Ser 603 may have functional significance, there has been no observed interaction of Ser 603 with glucose substrates. A torsional rotation of of the hydroxyl group brings about a much better distance for hydrogen bonding of the glucose O6. As a result of this observation, it can be assumed that Ser 603 may have some transient role during phosphorylation.<ref name="one" /> | In the <scene name='Sandbox_172/Mynewscene/2'>active site</scene> of hexokinase type I, Lys 621 and Asp 657 show the hydrogen-bonding distance in which a reactive O6 hydroxyl is situated in between. Here Lys 621 functions to aid the transfer of the phosphate moiety which is negatively charged; Asp 657 serves as a catalytic base or to position the glucose O6 correctly for phosphoryl transfer to take place. Though it may seem that Ser 603 may have functional significance, there has been no observed interaction of Ser 603 with glucose substrates. A torsional rotation of of the hydroxyl group brings about a much better distance for hydrogen bonding of the glucose O6. As a result of this observation, it can be assumed that Ser 603 may have some transient role during [http://en.wikipedia.org/wiki/phosphorylation phosphorylation].<ref name="one" /> | ||
===Regulatory Binding Site=== | ===Regulatory Binding Site=== | ||
As glucose-6-phosphate is being produced it binds to either one of the domains on hexokinase type I. On domain 1, the phosphate moiety is surrounded by Ser 88, Thr 232, and Ser 415. The presence of these three residues generate an anion binding site that is approximately 5.6 Å to the 6 hydroxyl of the glucose that is bound.<ref name="one" /> | As glucose-6-phosphate is being produced it binds to either one of the domains on hexokinase type I. On domain 1, the phosphate moiety is surrounded by Ser 88, Thr 232, and Ser 415. The presence of these three residues generate an anion binding site that is approximately 5.6 Å to the 6 hydroxyl of the glucose that is bound.<ref name="one" /> | ||
