Sandbox Reserved 770: Difference between revisions
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The central core within each monomer of PAL contains three central alpha helices of triple-coiled coils (Helix 3,Helix 4, and Helix 7), improving its rigidity similar to fibrous proteins in keratin. The three core helices are oriented with similarly aligned dipoles to create an electro-positive platform for cofactor 3,5-dihydro-5-methylidene-4H-imidazol-4-one (MIO) to anchor through noncovalent bonding, shown in Figure 4b. Covalent linkages between cofactor MIO and PAL backbone act to direct the C-terminus of MIO to an alpha helix's N-terminus, creating a loop, thus the helix's positive pole points toward the cofactor and the active site. PAL active site contains a highly conserved Ala-Ser-Gly triad. Post-translational modification of an electrophilic prostetic group MIO formed autocatalytically by cyclization and dehydration of PAL's active site. MIO provides the surface for phenylalanine conversion to produce trans-cinnamic acid and ammonia. | The central core within each monomer of PAL contains three central alpha helices of triple-coiled coils (Helix 3,Helix 4, and Helix 7), improving its rigidity similar to fibrous proteins in keratin. The three core helices are oriented with similarly aligned dipoles to create an electro-positive platform for cofactor 3,5-dihydro-5-methylidene-4H-imidazol-4-one (MIO) to anchor through noncovalent bonding, shown in Figure 4b. Covalent linkages between cofactor MIO and PAL backbone act to direct the C-terminus of MIO to an alpha helix's N-terminus, creating a loop, thus the helix's positive pole points toward the cofactor and the active site. PAL active site contains a highly conserved Ala-Ser-Gly triad. Post-translational modification of an electrophilic prostetic group MIO formed autocatalytically by cyclization and dehydration of PAL's active site. MIO provides the surface for phenylalanine conversion to produce trans-cinnamic acid and ammonia. | ||
Most of the conserved active site residues are contained within seven stabilizing alpha helices. Six positive alpha helices point toward the active site in association with MIO cofactor. This association will not only increase the electrophilicity of MIO, but also increases he positive charge of Lys residue 468. The positive poles stabilize the carbanion intermediate's negative charge introduced by the elimination unimolecular conjugate base (E1cB) mechanism of substrate phenylalanine, promoting the interactions between the negatively charged carboxylate end of the substrate. Promoting this interaction will subsequently stabilize the carbanion intermediate as well. < | Most of the conserved active site residues are contained within seven stabilizing alpha helices. Six positive alpha helices point toward the active site in association with MIO cofactor. This association will not only increase the electrophilicity of MIO, but also increases he positive charge of Lys residue 468. The positive poles stabilize the carbanion intermediate's negative charge introduced by the elimination unimolecular conjugate base (E1cB) mechanism of substrate phenylalanine, promoting the interactions between the negatively charged carboxylate end of the substrate. Promoting this interaction will subsequently stabilize the carbanion intermediate as well. <ref name=rutgers>http://maptest.rutgers.edu/drupal/?q=node/408</ref> | ||
==References== | ==References== | ||
<references /> | <references /> | ||
