Figure 1. TmpL is a putative membrane flavoprotein.

(A) Domain organization of TmpL. The predicted protein encoded by the tmpL gene is comprised of 1025 amino acid residues. This protein contains an AMP-binding domain, six putative transmembrane domains, and a FAD/NAD(P)-binding domain. The bottom picture shows predicted topological map of the TmpL protein. Regions of TmpL proposed to be hydrophobic membrane-spanning domains or hydrophilic domains facing the cytosol or subcompartmental matrix were identified using the TMHMM (http://www.cbs.dtu.dk/services/TMHMM-2.0/) and PRED-TMR (http://athina.biol.uoa.gr/PRED-TMR2/). (B) UV-visible spectra of TmpL partial recombinant protein containing FAD/NAD(P)-binding region. The absorbance spectrum shown indicates that the protein contains bound flavin (black line), demonstrating that TmpL is a FAD/NAD(P)-binding flavoprotein. Bovine serum albumin (BSA) was used as a non-flavin binding protein control (blue line). A solution of the FAD-incubated protein (2.0 mg ml⁻¹) in 50 mM sodium phosphate buffer, pH 7.5, was analyzed.