Description |
When this molecule is placed in low pH environment it undergoes a dramatic conformational change that almost amounts to the protein unfolding and then refolding with a new conformation. Parts of the protein move up to100 A. Most of the protein is affected by the motion and there is no clear 'motionless' core. The most invariant part of the protein appears to be a helical segment (helix C) packed againt two equivalent helices in other subunits in a a coiled-coil fashion. In the conformational change, residues N-terminal to this helix relocate and change into a helical conformation (to form helices A and B). This essentially extends helix C in the N-terminal direction. Conversely, the helix directly connected to the C-terminal side of helix C in the high-pH form (helix D) becomes partially an extended structure and relocates so that in the low pH-form it is antiparallel to helix C. |
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