Comparison of the putative topological organization of bacterial and mitochondrial TSPO.

(a) Pseudomonas fluorescens MF37 bactTSPO. (b) BactTSPO from Rhodobacter sphaeroides 2.4.1 recalculated from Yeliseev and Kaplan [12]. (c) Mitochondrial TSPO [13]. P. fluorescens MF37 bactTSPO has a typical five transmembrane helix structure, a larger L1 intra-cytoplasmic loop, and an extended cytoplasmic C-terminal end. In contrast, the extracellular N-terminal end is absent, and a peptidoglycane binding domain signature is present between the L2 loop and H3 transmembrane domain.