Spotlight on…Tracy Palmer

Extract

1. What is your current research addressing and what impact may this research have on the wider field?

My group works on mechanisms of protein transport in bacteria. Since I started my independent career in 1996, I have been interested in understanding how bacteria assemble the complex metalloenzymes that are essential for respiration. My work, alongside that of colleagues in the UK and Canada, helped to define the twin arginine protein transport (Tat) system in the model organism Escherichia coli (Sargent et al.1998; Weiner et al.1998). The Tat pathway transports folded proteins across the bacterial cytoplasmic membrane and substrates are recognised by the Tat machinery because they have an N-terminal signal peptide containing a conserved twin-arginine motif (Berks 1996). There are some 28 or so Tat substrate proteins in E. coli, and approximately two-thirds of them bind redox cofactors non-covalently (Palmer and Berks 2012). These proteins have their cofactors inserted and fold in the cytoplasm, sometimes also interacting with partner subunits, prior to translocation across the membrane through the Tat machinery (Jack et al.2004). Since folded Tat substrate proteins have very different sizes, the Tat system must accommodate the varying sized cargo without causing an uncontrolled leak of water or ions which would kill the cell.