Site Specific Protein Dynamics Probed by Ultrafast Infrared Spectroscopy of a Noncanonical Amino Acid

Christopher R. Hall, Jinnette Tolentino Collado, James N. Iuliano, Agnieszka Gil, Katrin Adamczyk, Andras Lukacs, Gregory M. Greetham, Igor Sazanovich, Peter J. Tonge, Stephen R. Meech

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Abstract

Real-time observation of structure change associated with protein function remains a major challenge. Ultrafast pump-probe methods record dynamics in light activated proteins, but the assignment of spectroscopic observables to specific structure changes can be difficult. The BLUF (blue light using flavin) domain proteins are an important class of light sensing flavoprotein. Here we incorporate the unnatural amino acid (UAA) azidophenylalanine (AzPhe) at key positions in the H-bonding environment of the isoalloxazine chromophore of two BLUF domains, PixD and AppABLUF; both proteins retain the red shift on irradiation characteristic of photoactivity. Steady state and ultrafast time resolved infrared (TRIR) difference measurements of the azido mode reveal site-specific information on the nature and dynamics of light driven structure change. AzPhe dynamics are thus shown to be an effective probe of BLUF domain photoactivation, revealing significant differences between the two proteins, and a differential response of the two sites to chromophore excitation.
Original languageEnglish
Pages (from-to)9592-9597
Number of pages6
JournalJournal of Physical Chemistry B
Volume123
Issue number45
Early online date9 Oct 2019
DOIs
Publication statusPublished - 14 Nov 2019

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