The retinal binding protein family: a powerful template for design and discovery

Title: The retinal binding protein family: a powerful template for design and discovery.The field of protein design has incredible potential for the development of myriad new andimproved chemical and biochemical function, from the development of powerful new catalyststo new biological tools for the detection and treatment of disease. It can also be a valuable toolfor understanding the structure, function and biophysics of proteins. We have focused on usingmembers of the intracellular lipid binding protein (iLBP) family as templates for protein design,due to their small size, relative stability to mutation, ease of structural study and comparativelylarge internal binding cavity, suitable to binding a wide range of large hydrophobic ligands. Wehave focused on the study of chromophore-bound proteins that mimic the rhodopsin family inthat binding of an aldehyde results in conjugated protonated Schiff base (PSB) formation. Theconjugated PSB’s absorbance is exquisitely sensitive to the protein electrostatic environment,allowing us to control absorbance, sometimes over a 200 nm range. It also offers the potentialof photoswitching via protonation/deprotonation of the PSB. We have used these properties tocreate new fluorescent proteins with a wide variety of properties, including near IR emission,photoswitching over an adjustable range of wavelengths, large Stokes shift FP’s to name a few.We have also used the system to study the detailed mechanisms of wavelength tuning andphotoisomerization. This talk will focus on the unravelling of the mechanisms of these systemsstructurally, where we are able to see photoswitching happen in the crystal at atomicresolution. In the course of this work we have discovered how small structural changes can leadto enormous, dynamic changes in pKa within a protein binding pocket.