Using light to control the form-function relationship of enzymes

COLL 543

C. Ted Lee, tedlee@usc.edu, Andrea Hamill, ahamill@usc.edu, and Serena Wang, shaochuw@usc.edu. Department of Chemical Engineering and Materials Science, University of Southern California, 925 Bloom Walk, Los Angeles, CA 90089-1211
A means to control alpha-chymotrypsin association and activity with light illumination has been developed using the interaction of the protein with a photoresponsive surfactant. Upon exposure to the appropriate wavelength of light, the azobenzene surfactant undergoes a reversible photoisomerization, with the visible-light (trans) form being more hydrophobic than the UV-light (cis) form. As a result, surfactant binding to the protein and, thus, protein association and activity can be tuned with light. Small-angle neutron scattering (SANS) data indicate that under visible light the protein exists as the monomer (active site exposed), while under UV-light the hexamer form is present (preventing access to the active site). Thus, this novel ability to control enzyme form with light (i.e., quaternary structure) can in turn be used to photo-control enzyme function (i.e., activity). This control of the enzyme form-function relationship is completely photo-reversible, providing a novel method to initiate turnover.