Lipids Activate SecA for High Affinity Binding to the SecYEG Complex.

Protein translocation across the bacterial cytoplasmic membrane is an essential process catalyzed predominantly by the Sec translocase. This system consists of the membrane-embedded protein-conducting channel SecYEG, the motor ATPase SecA, and the heterotrimeric SecDFyajC membrane protein complex. Previous studies suggest that anionic lipids are essential for SecA activity and that the N terminus of SecA is capable of penetrating the lipid bilayer.

LmrR-mediated gene regulation of multidrug resistance in Lactococcus lactis.

Multidrug resistance (MDR) in Lactococcus lactis is due to the expression of the membrane ATP-binding cassette (ABC) transporter LmrCD. In the absence of drugs, the transcriptional regulator LmrR prevents expression of the lmrCD operon by binding to its operator site. Through an autoregulatory mechanism LmrR also suppresses its own expression.

Purification and functional reconstitution of the bacterial protein translocation pore, the SecYEG complex.

In bacteria, proteins are secreted across the cytoplasmic membrane by a protein complex termed translocase. The ability to study the activity of the translocase in vitro using purified proteins has been instrumental for our understanding of the mechanisms underlying this process. Here, we describe the protocols for the purification and reconstitution of the SecYEG complex in an active state into liposomes.

The active protein-conducting channel of Escherichia coli contains an apolar patch.

Protein translocation across the cytoplasmic membrane of Escherichia coli is mediated by translocase, a complex of a protein-conducting channel, SecYEG, and a peripheral motor domain, SecA. SecYEG has been proposed to constitute an aqueous path for proteins to pass the membrane in an unfolded state. To probe the solvation state of the active channel, the polarity sensitive fluorophore N-((2-(iodoacetoxy)ethyl)-N-methyl) amino-7-nitrobenz-2-oxa-1,3-diazole was introduced at specific positions in the C-terminal region of the secretory protein proOmpA.

GTP hydrolysis of cell division protein FtsZ: evidence that the active site is formed by the association of monomers.

The essential prokaryotic cell division protein FtsZ is a tubulin homologue that forms a ring at the division site. FtsZ forms polymers in a GTP-dependent manner. Recent biochemical evidence has shown that FtsZ forms multimeric structures in vitro and in vivo and functions as a self-activating GTPase.