Characterization of the annular lipid shell of the Sec translocon

Biochim Biophys Acta. 2015 Oct;1848(10 Pt A):2050-6. doi: 10.1016/j.bbamem.2015.06.024. Epub 2015 Jun 27.


The bacterial Sec translocase in its minimal form consists of a membrane-embedded protein-conducting pore SecYEG that interacts with the motor protein SecA to mediate the translocation of secretory proteins. In addition, the SecYEG translocon interacts with the accessory SecDFyajC membrane complex and the membrane protein insertase YidC. To examine the composition of the native lipid environment in the vicinity of the SecYEG complex and its impact on translocation activity, styrene-maleic acid lipid particles (SMALPs) were used to extract SecYEG with its lipid environment directly from native Escherichia coli membranes without the use of detergents. This allowed the co-extraction of SecYEG in complex with SecA, but not with SecDFyajC or YidC. Lipid analysis of the SecYEG-SMALPs revealed an enrichment of negatively charged lipids in the vicinity of SecYEG, which in detergent assisted reconstitution of the Sec translocase are crucial for the translocation activity. Such lipid enrichment was not found with separately extracted SecDFyajC or YidC, which demonstrates a specific interaction between SecYEG and negatively charged lipids.

Keywords: Lipid–protein interaction; SMALP; Sec translocon; Styrene-maleic acid; Translocation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenosine Triphosphatases / chemistry*
  • Adenosine Triphosphatases / ultrastructure
  • Bacterial Proteins / chemistry*
  • Bacterial Proteins / ultrastructure
  • Enzyme Activation
  • Escherichia coli / enzymology*
  • Escherichia coli Proteins / chemistry*
  • Lipid Bilayers / chemistry*
  • Maleates / chemistry
  • Membrane Transport Proteins / chemistry*
  • Membrane Transport Proteins / ultrastructure
  • Proteolipids / chemistry*
  • SEC Translocation Channels
  • SecA Proteins
  • Static Electricity
  • Styrene / chemistry


  • Bacterial Proteins
  • Escherichia coli Proteins
  • Lipid Bilayers
  • Maleates
  • Membrane Transport Proteins
  • Proteolipids
  • SEC Translocation Channels
  • proteoliposomes
  • Styrene
  • maleic acid
  • Adenosine Triphosphatases
  • SecA Proteins