Research ArticleBIOPHYSICS

Dynamic interactions between a membrane binding protein and lipids induce fluctuating diffusivity

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Science Advances  20 Jan 2017:
Vol. 3, no. 1, e1601871
DOI: 10.1126/sciadv.1601871

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Abstract

Pleckstrin homology (PH) domains are membrane-binding lipid recognition proteins that interact with phosphatidylinositol phosphate (PIP) molecules in eukaryotic cell membranes. Diffusion of PH domains plays a critical role in biological reactions on membrane surfaces. Although diffusivity can be estimated by long-time measurements, it lacks information on the short-time diffusive nature. We reveal two diffusive properties of a PH domain bound to the surface of a PIP-containing membrane using molecular dynamics simulations. One is fractional Brownian motion, attributed to the motion of the lipids with which the PH domain interacts. The other is temporally fluctuating diffusivity; that is, the short-time diffusivity of the bound protein changes substantially with time. Moreover, the diffusivity for short-time measurements is intrinsically different from that for long-time measurements. This fluctuating diffusivity results from dynamic changes in interactions between the PH domain and PIP molecules. Our results provide evidence that the complexity of protein-lipid interactions plays a crucial role in the diffusion of proteins on biological membrane surfaces. Changes in the diffusivity of PH domains and related membrane-bound proteins may in turn contribute to the formation/dissolution of protein complexes in membranes.

Keywords
  • Anomalous diffusion
  • Peripheral membrane proteins
  • Pleckstrin homology domains
  • Phosphatidyl-inositol-phosphate
  • Molecular dynamics simulations

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