<p>Text S2. ABC Transporters and Energy-Linked Pathway Proteins Co-purifies with </p><p>YhjD</p><p>In addition to the LPS interactions (Table S1), YhjD also interacts with MalEKY, a maltose transport ATP-Binding Cassette (ABC) superfamily of transporters [1], a periplasmic-binding component of the ABC superfamily phosphate transporter (PhoS), and MglAB, a - methylgalactoside ATP-binding component of the ABC transporters [1]. Given that the ABC transporters are ubiquitous membrane proteins, co-purification of ABC transporters with YhjD suggest a common intermediate to these reactions which would affect translocation of diverse substrates across the cell membrane.</p><p>The other potential interactions of YhjD include the members of trimethylamine N-oxide </p><p>(TMAO) reductase proteins TorATZ in the respiratory system (Table S1). During respiration, E. coli use TMAO as an alternative terminal electron acceptor [2]. The TorA protein is located in the periplasm and is the terminal reductase that receives electrons from the TorC protein [3], while TorT, a member of the new periplasmic binding protein family, triggers the Tor respiratory system up on TMAO induction [4]. The TorZ protein represents a third TMAO respiratory system in E. coli [5]. These interactions suggest that YhjD is also involved in some capacity with diverse energy-linked pathways.</p><p>References</p><p>1. Wu LF, Mandrand-Berthelot MA (1995) A family of homologous substrate-binding proteins with a broad range of substrate specificity and dissimilar biological functions. Biochimie 77: 744-750. 2. Gennis, Stewart V (1996) Respiration. In Escherichia coli and Salmonella; Neidhardt FC, editor. Washington, DC: : American Society for Microbiology Press. 217–261. p.</p><p>1 3. Gon S, Jourlin-Castelli C, Theraulaz L, Mejean V (2001) An unsuspected autoregulatory pathway involving apocytochrome TorC and sensor TorS in Escherichia coli. Proc Natl Acad Sci U S A 98: 11615-11620. 4. Baraquet C, Théraulaz L, Guiral M, Lafitte D, Méjean V, et al. (2006 ) TorT, a member of a new periplasmic binding protein family, triggers induction of the Tor respiratory system upon trimethylamine N-oxide electron-acceptor binding in Escherichia coli. J Biol Chem 281: 189-199 5. Gon S, Patte JC, Mejean V, Iobbi-Nivol C (2000) The torYZ (yecK bisZ) operon encodes a third respiratory trimethylamine N-oxide reductase in Escherichia coli. J Bacteriol 182: 5779- 5786.</p><p>2</p>