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Arrestin (Dr. Martha Sommer)

Dr. Sommer’s group works

  • on the structure and function of arrestin and
  • the regulatory protein of the G protein-coupled receptors (GPCR), the largest family of cell-surface receptors in humans.

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Workgroup Arrestin

Dr. Sommer’s research focuses on the following topics:

  • Arrestin structure and function,
  • Molecular mechanism of arrestin activation by GPCRs,
  • Dynamics of arrestin-GPCR interactions.


A small family of arrestin proteins (4 members) binds to and regulates hundreds of different G-protein coupled receptors (GPCRs). GPCRs constitute the largest family of cell-surface receptors and play a role in nearly all physiological and sensory systems in the human body. Not surprisingly, GPCRs are the target of nearly half of all prescribed drugs. Arrestin-receptor interactions lead to deactivation, internalization, and intracellular trafficking of the receptor. Arrestin is also a signalling protein itself, by its ability to scaffold a wide array of kinases, phosphatases, ubiquitin ligases, transcription factors, and others.Our research focuses on elucidating the molecular details of how arrestins bind to receptors and the functional consequences of these interactions. We apply a wide array of different biochemical and biophysical techniques in order to observe how arrestin interacts with the prototypical GPCR rhodopsin (the photoreceptor of the rod cell) as well as other GPCRs. In particular we use site-directed fluorescence spectroscopy to observe conformational changes in defined locations on arrestin. Our long-term goal is to understand how the flexible structure of arrestin bestows such a versatility of functional.

Biophysical methods

The Sommer lab applies a wide array of biochemical and biophysical methods, for example:

  • the isolation of rhodopsin from native tissue, and the expression / purification of other GPCRs and arrestins from cell culture,
  • site-directed mutagenesis and labelling,
  • steady-state and time-resolved fluorescence spectroscopy and
  • molecular dynamics simulation and protein crystallography (in collaboration)