Sandbox Reserved 197: Difference between revisions
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==='''Disulfide Bonds'''=== | ==='''Disulfide Bonds'''=== | ||
Another important feature of the folding of RNase A is the presence of four disulfide bonds. These bonds contribute to the thermal stability and the rate of folding of RNase A. The residues involved in these linkages include <scene name='Sandbox_Reserved_197/Cys26-cys84/6'>Cys26-Cys84</scene>, <scene name='Sandbox_Reserved_197/Cys58-cys110/6'>Cys58-Cys110</scene>, <scene name='Sandbox_Reserved_197/40-95_disulfide_native_form/ | Another important feature of the folding of RNase A is the presence of four disulfide bonds. These bonds contribute to the thermal stability and the rate of folding of RNase A. The residues involved in these linkages include <scene name='Sandbox_Reserved_197/Cys26-cys84/6'>Cys26-Cys84</scene>, <scene name='Sandbox_Reserved_197/Cys58-cys110/6'>Cys58-Cys110</scene>, <scene name='Sandbox_Reserved_197/40-95_disulfide_native_form/8'>Cys40-Cys95</scene>, and <scene name='Sandbox_Reserved_197/Cys65-cys72/7'>Cys65-Cys72</scene>. Cys26-Cys84 and Cys58-Cys110 stabilize an interaction between an α-helix and a β-sheet which is the main contributor to the thermodynamic stability of the enzyme. | ||
Measurements of protein activity upon removal of disulfide bridges show that the change in enzymatic activity is very small and that not all disulfide bridges are essential for the structure or the reactivity of the protein. However, removal of disulfide bonds does destabilize the hydrophobic core and decreases the rate of folding. RNase A actually has a rate-determining three-disulfide intermediate. An analog of this, <scene name='Sandbox_Reserved_197/C40-95a_variant/8'>C[40,95]A</scene>, shows RNase A, missing the disulfide bond, Cys40-Cys95, that would normally occur here. In the variant, only 3 disulfide bonds are present, but the overall structure is only changed slightly. The differences occur in residues in close proximity to the location of the missing disulfide bond, <scene name='Sandbox_Reserved_197/Residues_34-45/1'>34-45</scene> and <scene name='Sandbox_Reserved_197/Residues_83-101/1'>83-101</scene>, where there are increased levels of disorder and a destabilized hydrophobic core. | Measurements of protein activity upon removal of disulfide bridges show that the change in enzymatic activity is very small and that not all disulfide bridges are essential for the structure or the reactivity of the protein. However, removal of disulfide bonds does destabilize the hydrophobic core and decreases the rate of folding. RNase A actually has a rate-determining three-disulfide intermediate. An analog of this, <scene name='Sandbox_Reserved_197/C40-95a_variant/8'>C[40,95]A</scene>, shows RNase A, missing the disulfide bond, Cys40-Cys95, that would normally occur here. In the variant, only 3 disulfide bonds are present, but the overall structure is only changed slightly. The differences occur in residues in close proximity to the location of the missing disulfide bond, <scene name='Sandbox_Reserved_197/Residues_34-45/1'>34-45</scene> and <scene name='Sandbox_Reserved_197/Residues_83-101/1'>83-101</scene>, where there are increased levels of disorder and a destabilized hydrophobic core. | ||
==='''Summary'''=== | ==='''Summary'''=== | ||
