Milligram quantities of homogeneous recombinant full-length mouse Munc18c from Escherichia coli cultures

PLoS One. 2013 Dec 31;8(12):e83499. doi: 10.1371/journal.pone.0083499. eCollection 2013.

Abstract

Vesicle fusion is an indispensable cellular process required for eukaryotic cargo delivery. The Sec/Munc18 protein Munc18c is essential for insulin-regulated trafficking of glucose transporter4 (GLUT4) vesicles to the cell surface in muscle and adipose tissue. Previously, our biophysical and structural studies have used Munc18c expressed in SF9 insect cells. However to maximize efficiency, minimize cost and negate any possible effects of post-translational modifications of Munc18c, we investigated the use of Escherichia coli as an expression host for Munc18c. We were encouraged by previous reports describing Munc18c production in E. coli cultures for use in in vitro fusion assay, pulldown assays and immunoprecipitations. Our approach differs from the previously reported method in that it uses a codon-optimized gene, lower temperature expression and autoinduction media. Three N-terminal His-tagged constructs were engineered, two with a tobacco etch virus (TEV) or thrombin protease cleavage site to enable removal of the fusion tag. The optimized protocol generated 1-2 mg of purified Munc18c per L of culture at much reduced cost compared to Munc18c generated using insect cell culture. The purified recombinant Munc18c protein expressed in bacteria was monodisperse, monomeric, and functional. In summary, we developed methods that decrease the cost and time required to generate functional Munc18c compared with previous insect cell protocols, and which generates sufficient purified protein for structural and biophysical studies.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Codon / genetics
  • Escherichia coli / genetics
  • Escherichia coli / metabolism
  • Mice
  • Multiprotein Complexes / isolation & purification
  • Multiprotein Complexes / metabolism
  • Munc18 Proteins / biosynthesis*
  • Munc18 Proteins / genetics
  • Munc18 Proteins / metabolism
  • Protein Binding
  • Protein Engineering
  • Qa-SNARE Proteins / genetics
  • Qa-SNARE Proteins / metabolism
  • Recombinant Proteins / biosynthesis
  • Recombinant Proteins / genetics
  • Recombinant Proteins / metabolism
  • SNARE Proteins / metabolism
  • Sf9 Cells
  • Spodoptera
  • Thermodynamics

Substances

  • Codon
  • Multiprotein Complexes
  • Munc18 Proteins
  • Qa-SNARE Proteins
  • Recombinant Proteins
  • SNARE Proteins
  • Stxbp3 protein, mouse

Grants and funding

This research was supported by the National Health and Medical Research Council of Australia (NHMRC) program grant 535921 to JLM. AEW is an NHMRC Peter Doherty Fellow (569864), BMC is an Australian Research Council (ARC) Future Fellow (FT100100027) and JLM is an ARC Australian Laureate Fellow (FL0992138) and Honorary NHMRC Fellow. The IMB Mass Spectrometry Facility used in this research was funded in part through an ARC LIEF grant (LE110100186). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.