Biomedical subjects

R Ebner

Publications and source records attributed to R Ebner.

51 records · Page 3Linked to original sources

PubMed1988

Sugar permeases of the bacterial phosphoenolpyruvate-dependent phosphotransferase system: sequence comparisons.

The amino acyl sequences of eight permeases (enzymes II and enzyme II-III pairs) of the bacterial phosphoenolpyruvate:sugar phosphotransferase system (PTS) have been analyzed. All systems show similar sizes, and six of these systems exhibit the same molecular weight +/- 2%. Several exhibit sequence homology. Characteristic NH2-terminal and COOH-terminal sequences were found. The NH2-terminal leader sequences are believed to function in targeting of the permeases to the membrane, whereas the characteristic COOH-terminal sequences are postulated to mediate interaction with the energy-coupling protein phospho HPr. One of the systems, the one specific for mannose, exhibits distinctive characteristics. A pair of probable phosphorylation sites was detected in each of the five most similar systems, those specific for beta-glucosides, sucrose, glucose, N-acetylglucosamine, and mannitol. One of the two equivalent phosphorylation sites (proposed phosphorylation site 1) was located approximately 80 residues from the COOH terminus of each system. The other site (proposed phosphorylation site 2) was located approximately 440 residues from the COOH termini of the glucose and N-acetylglucosamine systems, approximately 320 residues from the COOH termini of the beta-glucoside and sucrose systems, and 381 residues from the COOH terminus of the mannitol system. Intragenic rearrangement during evolutionary history may account for the different positions of phosphorylation sites 2 in the different PTS permeases. More extensive intragenic rearrangements may have given rise to entirely different positions of phosphorylation in the glucitol, mannose, and lactose systems. A single, internal amphipathic alpha-helix with characteristic features was found in each of seven of the eight enzymes II. The lactose-specific enzyme III of Staphylococcus aureus was unique in possessing a COOH-terminal amphipathic alpha-helix rich in basic amino acyl residues. Possible functions for these amphipathic segments are discussed.

Amino Acid Sequence↗

PubMed1988

Hydatid cysts of the orbit. A review of 35 cases.

The authors reviewed 35 cases of orbital hydatid cysts, which represented 5% of orbital surgical cases seen from 1944 to 1985. The average age was 16 years (range, 2-57 years). Slowly progressive unilateral exophthalmos, with or without pain, was the most frequent clinical manifestation. Computed tomography (CT) of the orbit demonstrated a well-circumscribed mass. Ultrasonography showed an anechoic cystic mass. The parasitic membrane and contents were surgically removed through an orbital approach. Hydatid cysts should be included in the differential diagnosis of unilateral exophthalmos in patients from countries where echinococcosis is endemic. Preoperative recognition is important for planning an appropriate surgical treatment in avoiding complications.

Adolescent↗

PubMed1988

Plasmid-mediated sucrose metabolism in Escherichia coli K12: mapping of the scr genes of pUR400.

The scr genes located on plasmid pUR400 and responsible for sucrose (Scr) metabolism of Escherichia coli K12 and other enteric bacteria have been cloned on a 9.3 kb DNA fragment. The different genes were mapped by transposon insertion mutagenesis, by restriction endonuclease and deletion mapping, and the corresponding gene products were identified. Besides the known structural genes scrA, coding for an EnzymeII(Scr) (45 kD) of the phosphoenolypyruvate-dependent phosphotransferase system (PTS), and scrB, coding for a sucrose 6-phosphate hydrolase (invertase) (55 kD), two new structural genes were discovered. Gene scrK apparently codes for an intracellular and ATP-dependent fructokinase (39 kD), while scrY seems to code for a sucrose porin (58 kD) in the outer cell membrane. No genes for an Enzyme III(Scr) of the PTS or for (a) glycosyltransferase(s) were detected. The four genes form an scr operon (gene order, scrK scrY scrA scrB, transcription from K to B), regulated by a repressor (gene scrR, 37 kD) and inducible by sucrose, fructose and fructose-containing oligosaccharides.

DNA Restriction Enzymes↗

PubMed1988

DNA sequence of the gene scrA encoding the sucrose transport protein EnzymeII(Scr) of the phosphotransferase system from enteric bacteria: homology of the EnzymeII(Scr) and EnzymeII(Bgl) proteins.

The nucleotide sequence of the structural gene, scrA, which codes for sucrose-specific EnzymeII(Scr) (EII(Scr)) of the phosphoenolpyruvate-dependent carbohydrate:phosphotransferase system (PTS), was determined. EllScr requires an EnzymeIII, the product of the gene crr, for full activity. The gene scrA is preceded immediately by a classical Shine-Dalgarno sequence (AAGAGGGTA). It contains 1368 nucleotides with an increased GC-content (58%) corresponding to a polypeptide of 455 amino acid residues (Mr 47,500). The protein has the hydropathic profile (average hydropathy +0.82) of an integral membrane protein lacking extended alpha-helical structures and a signal peptide. Comparison with the sequence of the beta-glucoside-specific EnzymeII (EII(Bgl), 625 amino acids, Mr 66,480; Bramley and Kornberg, 1987a; Schnetz et al., 1987) revealed strong homologies between EiI(Scr) and the first 458 residues of EII(Bgl). The 162 carboxyterminal residues of EII(Bgl), however, showed a high homology with the sequence of EnzymeIII (Nelson et al., 1984), a homology also described recently by Bramley and Kornberg (1987b). The evolutionary and functional significance of the similarities with four other EnzymesII is discussed.

Amino Acid Sequence↗

PubMed1987

Malignant melanoma of the conjunctiva. Report of a case.

Malignant melanomas of the conjunctiva are extremely rare in children. The authors report an 11-year-old boy who had a nodule at the limbus in a pigmented area since early childhood. The lesion was excised and the diagnosis of atypical compound nevus was made. Five months later, the patient returned with multiple nodules in the bulbar and palpebral conjunctiva. One of the lesions was excised, and the diagnosis was malignant melanoma. He was lost for follow-up for 6 months; then he presented a large pigmented, vascularized mass protruding through the palpebral aperture. Results of systemic workup for metastatic disease were negative, and an exenteration was performed. A few months later, cervical lymphadenopathy developed followed by extensive metastatic disease.

Child↗

PubMed1983

Angle closure glaucoma as initial manifestation of melanocytoma of the optic disc.

A 44-year-old man had progressive visual loss and pain due to angle-closure glaucoma associated with a papillary pigmented lesion. The eye was enucleated because of intractable pain and the suspicion of a malignant tumor. Histologic and electron microscopic examination of the enucleated eye revealed a partially necrotic melanocytoma of the optic nerve. There was histologic evidence of vaso-occlusive disease within the optic nerve that resulted in ischemic necrosis of the tumor, hypoxic retinopathy and neovascular glaucoma. This report emphasizes that significant complications may occur in otherwise typical intraocular nevi.

Adult↗

PubMed1979