TspO of Rhodobacter sphaeroides

Abstract

The function and specific structural aspects of the tryptophan-rich sensory protein (TspO) of Rhodobacter sphaeroides 2.4.1 were studied using site-directed mutagenesis involving some 17 different amino acids. The choice of these amino acids changes was dictated from an analysis of the TspO family of proteins derived from the data bases. These studies demonstrated the importance of several highly conserved tryptophan residues in the sensory transduction pathway involving TspO through the proposed binding of an intermediate(s) in the tetrapyrrole biosynthesis pathway. These studies also revealed that the substitution of one or several of the amino acid residues dramatically affected, either directly or indirectly, the levels of TspO in the membranes of R. sphaeroides. Mounting evidence is presented suggesting that TspO normally forms a dimer within the bacterial outer membrane, and the dimer form of TspO may be the active form for TspO function. Because our earlier studies provided us with a functional framework within which to view these amino acid substitutions, we are able to suggest a preliminary model for TspO structure-function. Not only do these studies tell us more about TspO, but they also shed light on the TspO homologue, the drug-binding component of the mitochondrial peripheral benzodiazepine receptor. Mounting evidence draws numerous parallelism between these proteins and supports the significance of using TspO as a model for the structure and function of the mitochondrial protein.

Effects of Oxygen and Light Intensity on Transcriptome Expression in Rhodobacter sphaeroides 2.4.1

“…However, we suggest that these data may be explained by concluding that post-transcriptional controls, at the level of enzyme activity, may play a more prominent role in pigment production than previously suggested (51,52). Such a conclusion is also supported by some earlier studies in R. sphaeroides on PucC (25,53), CrtA (54), and TspO (55). Throughout these investigations, we caution that we are cognizant that posttranscriptional analyses, such as an analysis of the proteome, corresponding to most of these genes is lacking.…”

Structure of the Mg-Chelatase Cofactor GUN4 Reveals a Novel Hand-Shaped Fold for Porphyrin Binding

“…TspO and PBR are highly related to one another [43]. Interestingly, sequence alignment of these proteins with GUN4 reveals 40% similarity to TspO and 44% similarity to PBR (see Figure 2B).…”

Response characteristics of the mitochondrial DNA genome in developmental health and disease

“…Structural models place the N-terminus and two intramitochondrial loops (m1 and m2) in the periplasmic compartment, and C-terminus with two extramitochondrial loops (c1 and c2) in the cytosol (Joseph-Liauzin et al, 1998). As discussed earlier, molecular models place this topology insideout for the Bzrp versus its proteobacterial ortholog TspO (Yeliseev and Kaplan, 2000).…”

“…They form homodimers/polymers in homologous membranes (bacterial and outer mitochondrial) and are functionally interchangeable (e.g., the rat pk18 protein can restore function in TspO null proteobacteria); furthermore, both proteins have the capacity to control the transport of hemerelated metabolites (Taketani et al, 1995;Yeliseev and Kaplan, 2000;Delavoie et al, 2003;Wendler et al, 2003). Molecular models from the deduced amino acid sequence place the N-terminus of TspO on the cell exterior and its C-terminus facing the periplasmic compartment; however, evolution reverses the topology of pk18 to an inside-out configuration (Joseph-Liauzun et al, 1998;Yeliseev and Kaplan, 2000). This may position Bzrp to function as an oxygen-sensing signal generator in mammalian cells (O'Hara et al, 2003), as will be reviewed later.…”