Low protein binding tips and Eppendorf tubes (Axygen) were used to increase reproducibility.
In contrast to zippers, in which receptors interact at the kinase-binding tip, in this case the two receptor layers interacted at their membrane-proximal tips.
In the absence of CheA and CheW, trimers bind each other at their kinase-binding tips in antiparallel fashion to form superstable zippers.
Cytoplasmic chemoreceptors assemble into two hexagonally packed arrays interacting at their presumably ligand-binding tips.
In native arrays, trimers of receptor dimers form extended hexagonal arrays anchored in the membrane at their ligand-binding tips and associating laterally through networked CheA and CheW.
Again, as we observed for transmembrane chemoreceptors, the kinase-binding tips were well ordered, with decreasing order towards the middle of the sandwich.
One of the principles that emerges from these observations and others already in the literature is that with the exception of some crystal structures, for example the Thermatoga receptors, where the receptors were arranged in "hedgerows" of dimers, receptors always form trimers of dimers linked together tightly at their kinase-binding tips but splaying outward toward their ligand-binding tips.
In the absence of membrane binding, either through deletion of transmembrane domains or in endogenous cytoplasmic chemoreceptors, MCPs again form bilayers, but in these cases through interactions at the ends of the receptors distal to their CheA-binding tips.
The highest selective theophylline binding of TIPs was found to be 61%, 41% and 40% for MAA/EDMA, MAA/HEMA/EDMA and MAA/ACM/EDMA systems, respectively.
Such a possibility would explain our finding that increasing the amount of salt in solution suppresses GMPCPP lattice binding, while tip-tracking of growing GTP-tubulin ends is maintained.
