Conformational Ensembles from Experimental Data and Computer Simulations

Conformational Ensembles from Experimental Data

and Computer Simulations

Poster Abstracts

24-POS

Board 24

Photoinduced Electron-transfer Fluorescence Correlation Spectroscopy of the

Conformational Dynamics of Intrinsically Disordered Proteins

Joerg Enderlein

Georg August University, Goettingen, Lower Saxony, Germany.

Intrinsically disordered proteins (IDP) form a large and functionally important class of proteins

that lack an ordered three-dimensional structure. IDPs play an important role in cell signaling,

transcription, or chromatin remodeling. The discovery of IDPs has challenged the traditional

paradigm of protein structure which states that protein function depends on a well-defined three-

dimensional structure.

Due to their high conformational flexibility and the lack of ordered secondary structure, it is

challenging to study the flexible structure, dynamics and energetics of these proteins with

conventional methods. In our work, we employ photoinduced electron-transfer (PET) combined

with fluorescence correlation spectroscopy (FCS) for studying the conformational dynamics of

one specific class of IDPs: phenylalanine-glycine rich protein domains (FG repeats) which are

dominant building blocks within the pore of nuclear pore complexes. We us the peculiarity of the

fluorescent dye Atto655 that, when excited, it shows a quasi-instantaneous and high-efficient

electron transfer to a tryptophan in direct contact with the dye. By placing one tryptophan at a

specific position within a peptide chain that is labeled at its end with Atto655, one can use FCS

for measuring the contact pair formation rate between the labeled peptide end and the tryptophan

position. By moving the tryptophan position along the peptide chain, one thus maps the

conformational dynamics of the full peptide. We observe point contact formation rates of a few

hundred nanoseconds, and see a strong variation of the rate on the distance between dye and

tryptophan, as well as on total length of the peptide chain. We demonstrate that PET-FCS is

particularly useful for the measurement of fast intramolecular conformational dynamics of small

biomolecules where conventional methods such as single-molecule Förster Resonance Energy

Transfer fail due to steric reasons.