Garman lab: Interconversion of lysosomal enzyme specificities: Difference between revisions
No edit summary |
|||
| Line 17: | Line 17: | ||
Galactose vs. N-acetyl-galactosamine | Galactose vs. N-acetyl-galactosamine | ||
The initial <scene name='78/786673/Galnac/2'>scene in the 3D browser</scene> shows the sugar N-acetyl galactosamine. If you turn off the spinning (control below the spinning image) and hover over the atoms, you can learn which colors represent carbon, nitrogen and oxygen. | |||
== Structures shown on this page == | == Structures shown on this page == | ||
| Line 35: | Line 38: | ||
The researchers asked the following question: Is it possible to turn one enzyme into the other (in terms of reaction catalyzed)? Their hypothesis was that a simple swap of the two amino acids in the active site that are different would accomplish an interconversion of specificities. | The researchers asked the following question: Is it possible to turn one enzyme into the other (in terms of reaction catalyzed)? Their hypothesis was that a simple swap of the two amino acids in the active site that are different would accomplish an interconversion of specificities. | ||
To test this, they made variants called GAL(SA) and NAGAL(EL), in which one active site has the amino acids of the other active site and vice versa (by swapping the two residues that are different). The data obtained by enzyme kinetics supported their hypothesis; the preference for galactose vs N-acetyl galactosamine is swapped (not shown here, but the data is in their paper). Crystal structures (Fig. show how GAL(SA) is able to bind to either <scene name='78/786673/Fig2a_galnac_complex/2'>N-acetyl galactosamine</scene> or <scene name='78/786673/Galsa_gal/21'>galactose</scene>. Comparing the structures of the NAGAL: N-acetyl galactosamine complex and the GAL(SA): N-acetyl galactosamine complex shows that <scene name='78/786673/Galsa_nagal/2'>they bind the ligand in a very similar manner</scene>. | To test this, they made variants called GAL(SA) and NAGAL(EL), in which one active site has the amino acids of the other active site and vice versa (by swapping the two residues that are different). The data obtained by enzyme kinetics supported their hypothesis; the preference for galactose vs N-acetyl galactosamine is swapped (not shown here, but the data is in their paper [http://www.jbc.org/content/285/28/21560.full]). Crystal structures (Fig. show how GAL(SA) is able to bind to either <scene name='78/786673/Fig2a_galnac_complex/2'>N-acetyl galactosamine</scene> or <scene name='78/786673/Galsa_gal/21'>galactose</scene>. Comparing the structures of the NAGAL: N-acetyl galactosamine complex and the GAL(SA): N-acetyl galactosamine complex shows that <scene name='78/786673/Galsa_nagal/2'>they bind the ligand in a very similar manner</scene>. | ||
You can explore the structural data further by going through the figures below and clicking on the buttons. If during your exploration, you get lost or some figures behave strangely, press <scene name='78/786673/Galnac/2'>here</scene> first to reset the 3D browser and then try again. | You can explore the structural data further by going through the figures below and clicking on the buttons. If during your exploration, you get lost or some figures behave strangely, press <scene name='78/786673/Galnac/2'>here</scene> first to reset the 3D browser and then try again. | ||
===Figure 1=== | ===Figure 1=== | ||
| Line 94: | Line 95: | ||
===Figure 2: Structure of GAL(SA)=== | ===Figure 2: Structure of GAL(SA)=== | ||
GAL(SA) is derived from GAL by replacing actives site residues glutamate 203 with serine and leucine 206 with alanine. Having these smaller amino acids in the active site increases the substrate binding cavity, and makes the active site of αGAL(SA) very similar to that of αNAGAL. With these substitutions, the catalytic activity of GAL(SA) is more similar to NAGAL than to GAL (the data is not shown here, but can be found in the research paper). | GAL(SA) is derived from GAL by replacing actives site residues glutamate 203 with serine and leucine 206 with alanine. Having these smaller amino acids in the active site increases the substrate binding cavity, and makes the active site of αGAL(SA) very similar to that of αNAGAL. With these substitutions, the catalytic activity of GAL(SA) is more similar to NAGAL than to GAL (the data is not shown here, but can be found in the research paper [http://www.jbc.org/content/285/28/21560.full]). | ||
<scene name='78/786673/Fig2a_galnac_complex/2'>Panel A</scene>: in complex with N-acetyl galactosamine | <scene name='78/786673/Fig2a_galnac_complex/2'>Panel A</scene>: in complex with N-acetyl galactosamine | ||