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SpoVM localizes by sensing convex membrane surfaces

Wednesday, September 16, 2015 — Poster Session I

3:30 p.m. – 5:00 p.m.
FAES Terrace
NCI
MOLBIO-15

* FARE Award Winner

Authors

  • EY Kim
  • K Ramamurthi

Abstract

Understanding the mechanisms that determine how proteins localize within a cell has broad impacts, from biotechnology to human health. The small peptide SpoVM, expressed in Bacillus species during sporulation, localizes via a mechanism previously unobserved in prokaryotes: recognition of membrane curvature. Fluorescence microscopy of Bacillus expressing SpoVM-GFP shows almost exclusive localization to the convex surface of the forespore during sporulation, while a single amino acid mutation, SpoVM(P9A), results in promiscuity to all membrane surfaces. This mislocalization mutant results in a loss of function, and the sporulation efficiency drops by six orders of magnitude compared to the wild type. We have developed an in-vitro system to reconstitute the convex surface of the forespore by coating silica microbeads with a lipid bilayer. We then use flow cytometry to quantify binding of SpoVM-GFP in this in-vitro system. Using this assay, we have characterized the binding saturation and binding kinetics of SpoVM. These findings reveal detail in what may be a general mechanism for localizing proteins to the surfaces of organelles.

Category: Molecular Biology and Biochemistry