Biophysical Studies on how the N-terminal Part of Photoactive Yellow Protein Accelerates its Functional Dynamics

Abstract

     Photoactive yellow protein (PYP) is a blue-light receptor protein that regulates negative phototaxis in Halorhodospira halophila. Photo-illumination converts PYP into a long-lived intermediate state, called pB. The initial pG state of PYP is recovered spontaneously in ~1 second. Previous work showed that the N-terminal region of PYP is important for the rapid rate of pB decay in the PYP photocycle. Our recent results suggested that electrostatic interactions between the negative charge on the N-terminal part of PYP and the positively charge on its PAS core are important in the acceleration of pB decay. To test this proposal, we designed a PYP mutant in which the N-terminal region is positively charged. Currently mutagenic primers are being used to create this mutant PYP. We have already isolated wild type PYP for comparison with the mutant and found that its photocycle corresponds well to published results.  We report these data and describe the plan for the next step.