Fuzzy supertertiary interactions within PSD-95 enable ligand binding.

The scaffold protein PSD-95 links postsynaptic receptors to sites of presynaptic neurotransmitter release. Flexible linkers between folded domains in PSD-95 enable a dynamic supertertiary structure. Interdomain interactions within the PSG supramodule, formed by DZ3, H3, and uanylate Kinase domains, regulate PSD-95 activity.

Why Are Gly31, Gly33, and Gly35 Highly Conserved in All Fluorescent Proteins?

Green fluorescent protein (GFP)-like fluorescent proteins have been found in more than 120 species. Although the proteins have little sequence identity, Gly31, 33, and 35 are 87, 100, and 95% conserved across all species, respectively. All GFP-like proteins have a β-barrel structure composed of 11 β-sheets, and the 3 conserved glycines are located in the second β-sheet.

Red-emitting chimeric firefly luciferase for in vivo imaging in low ATP cellular environments.

Beetle luciferases have been adapted for live cell imaging where bioluminescence is dependent on the cellular availability of ATP, O, and added luciferin. Previous Photinus pyralis red-emitting variants with high K values for ATP have performed disappointingly in live cells despite having much higher relative specific activities than enzymes like Click Beetle Red (CBR). We engineered a luciferase variant PLR3 having a K value for ATP similar to CBR and ∼2.