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Biomedical subjects

S L Mueller

Publications and source records attributed to S L Mueller.

16 recordsLinked to original sources
PubMed2006

On the self-association potential of transmembrane tight junction proteins.

Tight junctions seal intercellular clefts via membrane-related strands, hence, maintaining important organ functions. We investigated the self-association of strand-forming transmembrane tight junction proteins. The regulatory tight junction protein occludin was differently tagged and cotransfected in eucaryotic cells. These occludins colocalized within the plasma membrane of the same cell, coprecipitated and exhibited fluorescence resonance energy transfer. Differently tagged strand-forming claudin-5 also colocalized in the plasma membrane of the same cell and showed fluorescence resonance energy transfer. This demonstrates self-association in intact cells both of occludin and claudin-5 in one plasma membrane. In search of dimerizing regions of occludin, dimerization of its cytosolic C-terminal coiledcoil domain was identified. In claudin-5, the second extracellular loop was detected as a dimer. Since the transmembrane junctional adhesion molecule also is known to dimerize, the assumption that homodimerization of transmembrane tight junction proteins may serve as a common structural feature in tight junction assembly is supported.

Animals↗
PubMed2004

Occludin binds to the SH3-hinge-GuK unit of zonula occludens protein 1: potential mechanism of tight junction regulation.

The interaction between tight junction proteins occludin and zona occludens protein 1 (ZO-1) was clarified. The sequence cc1 within the hinge region of ZO-1, connecting its SH3 and GuK domains, was identified as a new association site for the occludin C-terminus, core binding area GLRSSKRNLRKSR (mouse ZO-1(606-618)). Occludin also bound to the sequence H2 within GuK, core area HKLRKNNH (ZO-1(759-766)). In occludin, the binding core was ELSRLDKELDDYREESEEY (mouse occludin(455-473)). Helicity of the sequences was suggested by circular dichroism. Because basic residues in ZO-1, acidic residues in occludin (underlined), coiled-coil helix-forming leucine heptad motifs (bold) in occludin and, probably, in cc1 were essential, we conclude that interactions were both helical and ionic. Moreover, the GuK domain bound other GuK molecules, suggesting oligomerization of ZO-1. Generally, the assumption is supported that the SH3-hinge-GuK region represents a functional and regulatory unit in ZO-1 forming a multiprotein tight junction complex with occludin.

Amino Acid Sequence↗
PubMed1997

Identification and transcriptional analysis of a Treponema pallidum operon encoding a putative ABC transport system, an iron-activated repressor protein homolog, and a glycolytic pathway enzyme homolog.

We have characterized a 5.2-kilobase (kb) putative transport related operon (tro) locus of Treponema pallidum subsp. pallidum (Nichols strain) (Tp) encoding six proteins: TroA, TroB, TroC, TroD, TroR and Phosphoglycerate mutase (Pgm). Four of these gene products (TroA-TroD) are homologous to members of the ATP-Binding Cassette (ABC) superfamily of bacterial transport proteins. TroA (previously identified as Tromp1) has significant sequence similarity to a family of Gram-negative periplasmic substrate-binding proteins and to a family of streptococcal proteins that may have dual roles as substrate binding proteins and adhesins. TroB is homologous to the ATP-binding protein component, whereas TroC and TroD are related to the hydrophobic membrane protein components of ABC transport systems. TroR is similar to Gram-positive iron-activated repressor proteins (DesR, DtxR, IdeR, and SirR). The last open reading frame (ORF) of the tro operon encodes a protein that is highly homologous to the glycolytic pathway enzyme, Pgm. Primer extension results demonstrated that the tro operon is transcribed from a sigma 70-type promoter element. Northern analysis and reverse transcriptase-polymerase chain reactions provided evidence for the presence of a primary 1-kb troA transcript and a secondary, less abundant, troA-pgm transcript. The tro operon is flanked by a Holliday structure DNA helicase homolog (upstream) and two ORFs representing a purine nucleoside phosphorylase homolog and tpp15, a previously characterized gene encoding a membrane lipoprotein (downstream). The presence of a complex operon containing a putative ABC transport system and a DtxR homolog indicates a possible linkage between transport and gene regulation in Tp.

ATP-Binding Cassette Transporters↗
PubMed1986

Benzanthrins A and B, a new class of quinone antibiotics. II. Isolation, elucidation of structure and potential antitumor activity.

The benzanthrins, which were produced by Nocardia lurida, were extracted from the fermentation broth with CH2Cl2. Subsequent purification on Sephadex LH-20 and diolbonded silica gel, followed by countercurrent chromatography, afforded analytically pure benzanthrins A and B. FAB-MS revealed that benzanthrins A and B were isomeric. It was demonstrated through degradative and spectroscopic studies that the benzanthrins were di-glycosides of a trihydroxy benz[a]anthraquinone chromophore where one of the sugars was linked through carbon and the other through oxygen. Benzanthrins A and B differed in the stereochemistry of the O-glycosidic sugar. Both compounds inhibited the growth of Gram-positive bacteria and 9KB, 9PS and 9ASK tumor cells in tissue culture.

Animals↗
PubMed1984

Lysinomicin, a new aminoglycoside antibiotic. II. Structure and stereochemistry.

The structure of lysinomicin, a new aminocyclitol antibiotic, was established as 3-epi-2'-N-(L-beta-lysyl)-4',5'-didehydro-6'-de-C-methylfortimi cin B (1) on the basis of spectral evidence and chemical degradation of the antibiotic. In the course of the degradation of 1, three additional compounds with interesting biological properties were obtained: 3-epi-2'-N-(L-beta-lysyl)-6'-de-C-methylfortimicin B (4), 3-epi-4',5'-didehydro-6'-de-C-methylfortimicin B (6) and 3-epi-6'-de-C-methylfortimicin B (7).

Aminoglycosides↗
PubMed1978

Modification of seldomycin factor 5 at C-3'.

Attempted removal of the 3'-hydroxyl group of seldomycin factor 5 via displacement of a sulfonate ester has led to 3'-epi-seldomycin factor 5. Removal of the hydroxyl group has been effected by the Barton procedure. The antibacterial activity of 3'-epi- and 3'-deoxyseldomycin factor 5 against various aminoglycoside-resistant strains is discussed.

Anti-Bacterial Agents↗
PubMed1978

Biotransformation of lankamycin, darcanolide, and 11-acetyllankolide by a blocked mutant of the erythromcyin producing organism Streptomyces erythreus.

The biotransformation of lankamycin and congeners darcanolide and 11-acetylankolide by a blocked mutant of the erythromycin-producing organism Streptomyces erythreus, which cannot synthesize erythromycin without supplementation with erythromycin precursors, was investigated. Darcanolide and 11-acetyllankolide were converted into the corresponding 15-deoxy-15-oxo derivatives. Lankamycin was transformed to 15-deoxy-15-oxolankamycin, 4''-deacetyl-15-deoxy-15-oxolankamycin and 3'-de-O-methylankamycin. None of the derivatives possessed high antimicrobial activity.

Anti-Bacterial Agents↗
PubMed1977

A new aminoglycoside antibiotic complex--the seldomycins. III. The structures of seldomycin factors 1 and 2+.

The structures of seldomycin factors 1 and 2 have been determined by consideration of chemical degradation and spectral properties. Factor 1, also known as XK-88-1, is shown to be 6-O-(2-amino-2-deoxy-alpha-D-xylopyranosyl) paromamine (1) and factor 2, also known as XK-88-2, is shown to be 4'-deoxy-neamine (2). Mass spectral evidence has been obtained that suggests the most probable structure for seldomycin factor 3, also known as XK-88-3, is 6'-amino-6'-deoxyseldomycin factor 1 (12).

Amino Sugars↗
PubMed1977

Fortimicins A and B, new aminoglycoside antibiotics. III. Structural identification.

The structures of fortimicins A and B have been determined by PMR, CMR, mass spectra and CD combined with chemical degradations. Both antibiotics are pseudodisaccharides and incorporate a novel aminocyclitol, fortamine. In contrast to the diaminocyclitol moieties of known aminoglycosides, fortamine is a 1,4-diamine, contains both N- and O-methyl groups and possesses chiro stereochemistry. Both antibiotics are glycosides of 6-epi-purpurosamine B, but fortimicin A differs from fortimicin B by being a glycyl amide.

Aminoglycosides↗