화학공학소재연구정보센터
Journal of the American Chemical Society, Vol.135, No.21, 7861-7868, 2013
Electronic Measurements of Single-Molecule Catalysis by cAMP-Dependent Protein Kinase A
Single-molecule studies of enzymes open a window into their dynamics and kinetics. A single molecule of the catalytic domain of cAMP-dependent protein kinase (PKA) was attached to a single walled carbon nanotube device for long duration monitoring. The electronic recording clearly resolves substrate binding, ATP binding, and cooperative formation of PICA's catalytically functional, ternary complex. Using recordings of a single PICA molecule extending over 10 min and tens of thousands of binding events, we determine the full transition probability matrix and conversion rates governing formation of the apo, intermediate, and closed enzyme configurations. We also observe kinetic rates varying over 2 orders of magnitude from one second to another. Anti correlation of the on and off rates for PICA binding to the peptide substrate, but not ATP, demonstrates that regulation of enzyme activity results from altering the stability of the PKA substrate complex, not its binding to ATP. The results depict a highly dynamic enzyme offering dramatic possibilities for regulated activity, an attribute useful for an enzyme with crucial roles in cell signaling