the Tans Biophysics LabAMOLF, Amsterdam

Group members associated:

  • Fatemeh Moayed
  • Roeland van Wijk
  • Mohsin Naqvi
  • Mario Avellaneda Sarrio

How chaperone interactions affect protein folding pathways is a central problem in biology. With the use of optical tweezers and all-atom molecular dynamics simulations, we study the effect of chaperones on the folding and unfolding pathways of maltose binding protein (MBP) at the single-molecule level. We have shown that chaperone SecB binds to the extended or molten globulelike structure and retains MBP in this latter state. Thus during MBP translocation, no energy is required to disrupt stable tertiary interactions. We are currently investigating various other chaperone systems.

von Willebrand factor (VWF) multimers mediate primary adhesion and aggregation of platelets. VWF potency critically depends on multimer size, which is regulated by a feedback mechanism involving shear-induced unfolding of the VWF-A2 domain and cleavage by the metalloprotease ADAMTS-13. With the use of optical tweezers, we have shown that unfolding of A2 requires higher forces when calcium is present and primarily proceeds through a mechanically stable intermediate with non-native calcium coordination. Calcium further accelerates refolding markedly, in particular, under applied load. Metal coordination therefore improves force sensing by allowing reversible force switching under physiologically relevant hydrodynamic conditions.

Our group is continuously working on technical development to advance the state of the art of the optical tweezers for single molecule biophysics applications. We are also developing more efficient methods for tethering molecules for pulling experiments.

Research highlights:

  • "Reshaping of the conformational search of a protein by the chaperone trigger factor" - Nature 500, 98-101 (2013)
  • "Calcium modulates force sensing by the von Willebrand factor A2 domain" - Nat.Commun. 2, 385 1-9 (2011)
  • "Noise reduction by signal combination in Fourier space applied to drift correction in optical tweezers" - Rev.Sci.Instr. 82,115103 (2011)
  • "Direct Observation of Chaperone-Induced Changes in a Protein Folding Pathway" - Science 318:1458-1461 (2007)