Expression,purification and Characterization of the Escherichia coli integral membrane protein YajC

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 (yajcct). yajcct formed a compact structure rich in β-strands and existed as a trimer. © 2011 bentham science publishers ltd.