Sandbox Reserved 1101: Difference between revisions
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The dimerization of the spidroin by the NTD domain begins by a rearrangement of the five-helix bundle during the monomer to dimer transition. An acidification along the spinning duct results in a conformational change of the NTD. So, for the NTD dimerization, a lowering of pH from 7 to 6 is important. Then, a subunit selects a partner with a complementary binding interface. When the NTD forms a dimer, its positive and negative poles are opposed, creating an environment conducive to salt bridges formation. Moreover, dimerization is really triggered and stabilized by protonation of some residues. Studies have also shown that a lowering more important of the pH stabilize even more the dimer. The plasticity of the dimer interface could also be a factor of the conformational selection during transition from monomer to dimer or during the transition from loosely to stably dimer. | The dimerization of the spidroin by the NTD domain begins by a rearrangement of the five-helix bundle during the monomer to dimer transition. An acidification along the spinning duct results in a conformational change of the NTD. So, for the NTD dimerization, a lowering of pH from 7 to 6 is important. Then, a subunit selects a partner with a complementary binding interface. When the NTD forms a dimer, its positive and negative poles are opposed, creating an environment conducive to salt bridges formation. Moreover, dimerization is really triggered and stabilized by protonation of some residues. Studies have also shown that a lowering more important of the pH stabilize even more the dimer. The plasticity of the dimer interface could also be a factor of the conformational selection during transition from monomer to dimer or during the transition from loosely to stably dimer. | ||
===Interactions=== | ====Interactions==== | ||
*Principal interactions | *Principal interactions | ||
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===pH-dependent mechanism=== | ====pH-dependent mechanism==== | ||
In order to observe the pH-dependent NTD dimerization mechanism, a tryptophan fluorescence assay was used. The N. clavipes NTD contains a single tryptophan (Trp10) near the N terminus. During the transition from the NTD monomer to the NTD dimer, a conformational change occurs for Trp10 that increases its solvent exposure. As a consequence, a quenching of its fluorescence emission is observed. The transition from the NTD monomer to the NTD dimer occurs at pH 6,1. At pH above 6,1, NTD is in the form of monomer and the formation of dimer occurs after pH 6,1. | In order to observe the pH-dependent NTD dimerization mechanism, a tryptophan fluorescence assay was used. The N. clavipes NTD contains a single tryptophan (Trp10) near the N terminus. During the transition from the NTD monomer to the NTD dimer, a conformational change occurs for Trp10 that increases its solvent exposure. As a consequence, a quenching of its fluorescence emission is observed. The transition from the NTD monomer to the NTD dimer occurs at pH 6,1. At pH above 6,1, NTD is in the form of monomer and the formation of dimer occurs after pH 6,1. | ||
