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 occurs during the monomer to dimer transition. An acidification of the medium 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.

Different types of interactions occur between specific residues during the NTD dimerization. Asp40, Lys65, Asp39 and Glu84 residues have been identified as being particularly important.

In one side, Asp40 and Glu84 of subunit A engage in the intramolecular handshake interaction. Lys65 of subunit A and Asp39 of subunit B engage in a short-range intermolecular salt bridge of 2,6Å. In the other side, Asp40 of subunit A and Lys65 of subunit B engage in a short-range intermolecular salt bridge of 3,1Å. Asp39 is not involved in this part of the dimer.

The structure of N. clavipes dimer interface differs from those of other species due to the asymmetric nature of the interface and the involvement of Asp39. It has been reported that Asp39 is essential for the NTD dimerization in other species of spiders (16). The asymmetric nature and the difference of topology of the subunits allow the formation of salt bridges between Asp39 and Lys65 and between Asp40 and Lys65. These interactions make subunits alignment better. Acidic residues are conserved around residues Asp96 and Asp40 and this allows the variability in the interactions that take place to Lys65. This variability provides a mechanism for plasticity in the dimer interface allowing the transition from loosely to stably associated dimer.

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 occurs during the monomer to dimer transition. An acidification of the medium 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.
+Different types of interactions occur between specific residues during the NTD dimerization. Asp40, Lys65, Asp39 and Glu84 residues have been identified as being particularly important.
+In one side, Asp40 and Glu84 of subunit A engage in the intramolecular handshake interaction. Lys65 of subunit A and Asp39 of subunit B engage in a short-range intermolecular salt bridge of 2,6Å. In the other side, Asp40 of subunit A and Lys65 of subunit B engage in a short-range intermolecular salt bridge of 3,1Å. Asp39 is not involved in this part of the dimer.
+The structure of N. clavipes dimer interface differs from those of other species due to the asymmetric nature of the interface and the involvement of Asp39. It has been reported that Asp39 is essential for the NTD dimerization in other species of spiders (16). The asymmetric nature and the difference of topology of the subunits allow the formation of salt bridges between Asp39 and Lys65 and between Asp40 and Lys65. These interactions make subunits alignment better. Acidic residues are conserved around residues Asp96 and Asp40 and this allows the variability in the interactions that take place to Lys65. This variability provides a mechanism for plasticity in the dimer interface allowing the transition from loosely to stably associated dimer.