Identification of a cryptic N-terminal signal in Saccharomyces cerevisiae peroxisomal citrate synthase that functions in both peroxisomal and mitochondrial targeting.

Saccharomyces cerevisiae has three distinct citrate synthases, two located in mitochondria (mature Cit1p and Cit3p) and one in peroxisomes (mature Cit2p). While the precursor of the major mitochondrial enzyme, Cit1p, has a signal for mitochondrial targeting at its N-terminus (MTS), Cit2p has one for peroxisomal targeting (PTS1) at its C-terminus. We have previously shown that the N-terminal segment of Cit2p is removed during import into peroxisomes [Lee, H.S. et al. (1994) Kor. J. Microbiol. 32, 558-564], which implied the presence of an additional N-terminal sorting signal. To analyze the function of the N-terminal region of Cit2p in protein trafficking, we constructed the N-terminal domain-swapped versions of Cit1p and Cit2p. Both fusions, Cit1::Cit2 and Cit2::Cit1, complemented the glutamate auxotrophy caused by the double-disruption of the CIT1 and CIT2 genes. In addition, part of the Cit2::Cit1 fusion protein, as well as Cit1::Cit2, was shown to be transported into both mitochondria and peroxisomes. The subcellular localization of the recombinant fusion proteins containing various N-terminal segments of Cit2p fused to a mutant version of green fluorescent protein (GFP2) was also examined. As a result, we found that the 20-amino acid N-terminal segment of Cit2p contains a cryptic cleavable targeting signal for both peroxisomes and mitochondria. In addition, we show that the peroxisomal import process mediated by the N-terminal segment of Cit2p was not affected by the disruption of either PEX5 (encoding PTS1 receptor) or PEX7 (encoding PTS2 receptor).

Recombinant polioviruses expressing hepatitis B virus-specific cytotoxic T-lymphocyte epitopes.

T-cell immune response to recombinant poliovirus expressing foreign antigens has not been elucidated well. In order to investigate the potential use of poliovirus as a T-cell vaccine vector, we constructed recombinant polioviruses expressing HBV-derived CTL epitopes, HBsAg(28-39) (L(d)-restricted; IPQSLDSWWTSL) and HBc(93-100) (K(b)-restricted; MGLKFRQL) at the junction between the P2 and P3 regions, designated V3CDs and V3CDc, respectively. The V3CDs and V3CDc recombinant viruses replicated efficiently in HeLa cells and showed a similar infection profile to that of the wild-type Mahoney strain in one-step growth kinetics. Genetic stability analysis showed that V3CDc retained the foreign insert over twelve successive passages examined, whereas V3CDs lost part of the foreign insert after four passages. Our results indicated that the stability of the inserted foreign sequences was rather affected by their nucleotide sequence than by their length when located between the P2 and P3 regions. The junction between these nonstructural protein-coding regions is a novel site for the construction of replication-competent recombinant poliovirus. Immunization of BALB/c (H-2(d)) and C57BL/6 mice (H-2(b)) with V3CDs and V3CDc, respectively, elicited significant antigen-specific CTL responses to HBsAg(28-39) but not to HBcAg(93-100).

Direct imaging of the InSb001-c8 x 2 surface: evidence for large anisotropy of the reconstruction.

We have observed the InSb(001)-c(8 x 2) surface by using high-resolution transmission electron microscopy in the profile-imaging geometry. All images observed at temperatures up to 420 degrees C agree well with the c(8 x 2) model reported by Kumpf et al. [Phys. Rev. Lett. 86, 3586 (2001)]]. 1/30 sec real-time observations at 420 degrees C evidence that a part of the subsurface and surface layers (called a gull-type segment) undergo switching to and from a bulk configuration. The finding is suggestive of large anisotropy in the mean square displacement of the c(8 x 2) surface.

Comparison of tuberculous and pyogenic epididymal abscesses: clinical, gray-scale sonographic, and color Doppler sonographic features.

OBJECTIVE: The purpose of this study was to evaluate the capability of clinical, gray-scale sonographic, and color Doppler sonographic features for differentiating tuberculous and pyogenic epididymal abscesses. MATERIALS AND METHODS: Retrospective analysis was performed in 10 cases of tuberculous epididymal abscess and in 13 cases of pyogenic epididymal abscess. The following clinical, gray-scale sonographic, and color Doppler sonographic features were analyzed: patient's age; duration of symptoms; scrotal tenderness; presence of sinus tract; concurrent tuberculosis in other organs; location, size, and echogenicity of the abscess; hyperechoic rim; testicular involvement; hydrocele; and blood flow in the epididymal lesion. RESULTS: Tuberculous epididymal abscess had a longer duration of symptoms (p = 0.0001) and a lower frequency of scrotal tenderness (p = 0.0048) than pyogenic epididymal abscess. The size of the abscess was larger in tuberculous epididymal abscess than in pyogenic epididymal abscess (p = 0.0002). The degree of blood flow in the peripheral portion of the abscess was lower in tuberculous epididymal abscess (p = 0.001). The patient's age, location and echogeninicity of the abscess, presence of sinus tract, hyperechoic rim, testicular involvement, and hydrocele did not differ between the tuberculous and pyogenic epididymal abscesses. CONCLUSION: Some clinical findings, gray-scale sonography, and color Doppler sonography were useful in differentiating tuberculous epididymal abscess from pyogenic epididymal abscess. The presence of long-term scrotal swelling without tenderness and a lower degree of blood flow in the peripheral portion of a large abscess are suggestive of tuberculous epididymal abscess.