Glutamine switch

A glutamine switch mechanism for nucleotide selectivity by phosphodiesterases. Mol. Cell. 15, 279-86. 

Arp, D. J., and Zumft, W. G. (1983). L-Methionine-SR-Sulfoximine as a probe for the role of glutamine synthetase in nitrogenase switch-off by ammonia and glutamine in Rkodopseudomonas palustris. Arch. Microbiol. 134, 17—22. 

Figure 4 Residues within Ga that are critical to the GTP hydrolysis mechanism include arginine-178 and threonine-181 from switch I and glutamine-204 from switch II (colored as in Fig. 2 and numbered as in Ga i coordinates are from PDB record IGFI). Magnesium ion is highlighted in yellow. The planar anion aluminum tetrafluoride, which mimics the y-phosphate leaving group in the hydrolysis reaction, is depicted in metallic red. Note the position of serine-47, the target of phosphorylation by the Y. pestis protein kinase YpkA.

Template-o , which is a designed coiled coil. To encourage a conformational switch, residues at / positions were changed from glutamine to threonine to produce Template-ofT. Below 70 °C, the peptide is cK-helical and above this temperature it forms -structured amyloid-like fibrils. Cross-linking the peptides to achieve a )8-hairpin-like conformation increases amyloid fibril formation. 

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