The gold pellet was resuspended in 50 without braking. obtained by transient expression of fusion constructs with the green Fulvestrant R enantiomer fluorescent protein in Arabidopsis protoplasts, whereas AtStr2 was exclusively localized to the cytoplasm by this method. Three members of the single-domain AtStr were localized in the chloroplasts as demonstrated by transient expression of green fluorescent protein fusions in protoplasts and stomata, whereas the single-domain AtStr18 was shown to be cytoplasmic. The remarkable subcellular distribution of AtStr15 was additionally analyzed by transmission electron immunomicroscopy using a monospecific antibody against green fluorescent protein, indicating an attachment to the thylakoid membrane. The knowledge of the intracellular localization of the members of this multiprotein family will help elucidate their specific functions in the organism. All members in the sulfurtransferase (Str)/rhodanese protein family in archaea, eubacteria, and eukaryota are unified by characteristic well-defined sequence domains (Bordo and Bork, 2002). These domains are found as tandem repeats, with the C-terminal domain containing the active site Cys residue, as single-domain proteins or as members of multidomain proteins (Bordo and Bork, 2002). The 18 proteins identified in Arabidopsis which contain at least one Str signature were classified into six groups on the basis of their sequence homology (Bauer and Papenbrock, 2002; http://arabidopsis.org/info/genefamily/STR_genefamily.html). Group I consists of two Str proteins with two-domain; the five proteins in group VI contain only the C-terminal Str signature and thus possess similarity to the single-domain Str from bacteria. Strs catalyze the transfer of a sulfur atom from suitable sulfur donors to a nucleophilic acceptor. Specific biological roles for most members of this superfamily have not been established (Spallarossa et al., 2001). Proposed roles include cyanide detoxification (Vennesland et al., 1982), involvement in sulfate assimilation (Donadio et al., 1990), and mobilization of sulfur for iron-sulfur cluster biosynthesis or repair (Bonomi et al., 1977). The most studied and best characterized Str is bovine rhodanese (thiosulfate:cyanide Str, EC 2.8.1.1), which catalyzes in Fulvestrant R enantiomer vitro the transfer of a sulfane sulfur atom from thiosulfate to cyanide, leading to the formation of sulfite and thiocyanate (Westley, 1973). Strs have been identified in different compartments in living organisms. In seven Str proteins were identified; a single-domain Str, GlpE, is a cytoplasmic protein, whereas at least one two-domain Str was localized in the periplasm (Ray et al., 2000). In the cyanobacterium sp. strain PCC 7942, a rhodanese-like protein was localized to the periplasmic space and was suggested to play a role in the transport of specific sulfur compounds (Laudenbach et al., 1991). Fulvestrant R enantiomer In mammalia two different Str enzymes with 3-mercaptopyruvate and thiosulfate-specific activities have been identified which are characterized by different and including (wPS) or excluding (woPS) their putative targeting peptide sequences (Fig. 1; for an Rabbit Polyclonal to Collagen V alpha1 overview of the constructs see Table I). Colocalization of the AtStr1wPS/pGFP-N fluorescence with MitoTracker Orange fluorescence, a dye that is specifically enriched in mitochondria, in the same protoplasts using a confocal laser scanning microscope (CLSM) resulted in the same picture. A second control for mitochondrial intracellular localization was used: the targeting peptide of the mitochondrial protein, Ser hydroxymethyltransferase, was fused to the GFP protein, resulting in the same image as transient transformation with the AtStr1 fusion construct (data not shown). These results indicated import of the AtStr1 protein into the mitochondria (Fig. 1, A and B). The same localization results were obtained with a fluorescence microscope (Fig. 1D). The corresponding bright field picture visualizes the protoplast’s cell membrane, demonstrates the intactness of the protoplasts, and demonstrates the position of the chloroplasts (Fig. 1C). expressed without its putative targeting peptide sequence remained in the cytoplasm (Fig. 1F). The fusion construct of with the targeting peptide sequence and the GFP-encoding cDNA sequence at the 5 end (AtStr1wPS/pGFP-C) resulted in a fluorescence image identical to the transformed pGFP-C vector alone (data not shown). This indicates that the N-terminal targeting peptide is recognized by the import machinery of the mitochondria. Open in a separate window Figure 1. Subcellular localization of AtStr1 and AtStr2 GFP fusion constructs with and without signal peptide. A, Arabidopsis protoplasts were transformed with including its targeting peptide sequence (AtStr1wPS). Fluorescence images of the protoplasts were taken using a confocal laser scanning microscope. The GFP fluorescence was excited with the argon laser (488 nm) and detected at 515 nm to 520 nm. B, The same protoplast suspension was additionally stained with MitoTracker Orange CMTMRos. The fluorescence was excited with the green.