title: Expression, purification and characterization of the Escherichia coli integral membrane protein YajC.
abstract: Escherichia coli YajC is a small integral membrane protein with a single transmembrane helix. The gene yajC is part of the secD operon and the protein is identified in the SecDF-YajC complex. However, the exact function of YajC remains a mystery. While its function is usually discussed in the context of the SecDF-YajC complex, studies have shown that SecD/F, rather than YajC, are essential for those functions. Recently YajC is identified as the mysterious protein that co-crystallized with AcrB. To further investigate the structure of YajC, we expressed and purified the protein in a detergent solubilized state. The protein assumed a folded structure containing mixed α/β secondary structures, consistent with the structural prediction. Using signal Cys mutations and thiol-specific probes, we found the C-terminus of YajC was cytoplasmic, while the N-terminus of YajC was buried in the membrane. In addition, we expressed and purified a truncated fragment of YajC that corresponded to the C-terminal cytoplasmic domain (YajC(CT)). YajC(CT) formed a compact structure rich in β-strands and existed as a trimer.
authors.affiliation: Department of Chemistry, University of Kentucky, Lexington, KY 40506-0055, USA.
authors.forename: Jun
authors.initials: J
authors.lastname: Fang
authors.forename: Yinan
authors.initials: Y
authors.lastname: Wei
mesh_terms: D000595:Amino Acid Sequence; D019921:Biotinylation; D002462:Cell Membrane / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D004926:Escherichia coli; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000235:genetics* / Q000302:isolation & purification* / Q000378:metabolism; D015870:Gene Expression; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D011487:Protein Conformation; D017510:Protein Folding; D055503:Protein Multimerization; D012269:Ribosomal Proteins / Q000737:chemistry / Q000235:genetics* / Q000302:isolation & purification* / Q000378:metabolism; D013438:Sulfhydryl Compounds / Q000378:metabolism
chemical_list: D029968:Escherichia coli Proteins; D012269:Ribosomal Proteins; D013438:Sulfhydryl Compounds; C554198:YajL protein, E coli