title: Folding and self-association of atTic20 in lipid membranes: implications for understanding protein transport across the inner envelope membrane of chloroplasts.
abstract: BACKGROUND
  The Arabidopsis thaliana protein atTic20 is a key component of the protein import machinery at the inner envelope membrane of chloroplasts. As a component of the TIC complex, it is believed to form a preprotein-conducting channel across the inner membrane.
  
  
  RESULTS
  We report a method for producing large amounts of recombinant atTic20 using a codon-optimized strain of E. coli coupled with an autoinduction method of protein expression. This method resulted in the recombinant protein being directed to the bacterial membrane without the addition of a bacterial targeting sequence. Using biochemical and biophysical approaches, we were able to demonstrate that atTic20 homo-oligomerizes in vitro when solubilized in detergents or reconstituted into liposomes. Furthermore, we present evidence that the extramembranous N-terminus of the mature protein displays characteristics that are consistent with it being an intrinsically disordered protein domain.
  
  
  CONCLUSIONS
  Our work strengthens the hypothesis that atTic20 functions similarly to other small α-helical integral membrane proteins, such as Tim23, that are involved in protein transport across membranes.
authors.affiliation: Department of Biology, Wilfrid Laurier University, 75 University Avenue West, Waterloo, ON, N2L 3C5, Canada. camp0410@mylaurier.ca.|Current address: Department of Biology, University of Waterloo, Waterloo, ON, Canada. camp0410@mylaurier.ca.
authors.forename: James H
authors.initials: JH
authors.lastname: Campbell
authors.affiliation: Department of Chemistry & Biochemistry, Wilfrid Laurier University, Waterloo, ON, Canada. tuan@uoguelph.ca.|Biophysics Interdepartmental Group, University of Guelph, Guelph, ON, Canada. tuan@uoguelph.ca.
authors.forename: Tuan
authors.initials: T
authors.lastname: Hoang
authors.affiliation: Department of Chemistry & Biochemistry, Wilfrid Laurier University, Waterloo, ON, Canada. mjelokhani@wlu.ca.|Biophysics Interdepartmental Group, University of Guelph, Guelph, ON, Canada. mjelokhani@wlu.ca.
authors.forename: Masoud
authors.initials: M
authors.lastname: Jelokhani-Niaraki
authors.affiliation: Department of Biology, Wilfrid Laurier University, 75 University Avenue West, Waterloo, ON, N2L 3C5, Canada. msmith@wlu.ca.|Biophysics Interdepartmental Group, University of Guelph, Guelph, ON, Canada. msmith@wlu.ca.
authors.forename: Matthew D
authors.initials: MD
authors.lastname: Smith
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000096:biosynthesis / Q000737:chemistry*; D002736:Chloroplasts / Q000378:metabolism*; D004926:Escherichia coli; D007425:Intracellular Membranes / Q000378:metabolism*; D064267:Intrinsically Disordered Proteins / Q000096:biosynthesis / Q000737:chemistry; D008081:Liposomes; D026901:Membrane Transport Proteins / Q000096:biosynthesis / Q000737:chemistry*; D008969:Molecular Sequence Data; D010713:Phosphatidylcholines / Q000737:chemistry; D017510:Protein Folding; D055503:Protein Multimerization; D058849:Protein Refolding; D017434:Protein Structure, Tertiary; D021381:Protein Transport
chemical_list: D029681:Arabidopsis Proteins; D064267:Intrinsically Disordered Proteins; D008081:Liposomes; D026901:Membrane Transport Proteins; D010713:Phosphatidylcholines; C457764:Tic20 protein, Arabidopsis; C028694:1-palmitoyl-2-oleoylphosphatidylcholine