The extracellular polysaccharides (EPS) produced by lactic acid bacteria (LAB) are associated with the rheology, texture, and mouthfeel of fermented milk products, including yogurt. This study investigated the immunomodulatory effects of EPS purified from the culture supernatant of Lactobacillus delbrueckii ssp. bulgaricus (L. bulgaricus) OLL1073R-1. The crude EPS were prepared from the culture supernatant of L. bulgaricus OLL1073R-1 by standard chromatographic methods, and were fractionated into neutral EPS and acidic EPS (APS). Acidic EPS were further fractionated into high molecular weight APS (H-APS) and low molecular weight APS (L-APS). High molecular weight APS were shown to be phosphopolysaccharides containing D-glucose, D-galactose, and phosphorus. Stimulation of mouse splenocytes by H-APS significantly increased interferon-gamma production, and, moreover, orally administered H-APS augmented natural killer cell activity. Oral administration of yogurt fermented with L. bulgaricus OLL1073R-1 and Streptococcus thermophilus OLS3059 to mice showed a similar level of immunomodulation as H-APS. However, these effects were not detected following administration of yogurt fermented with the starter combination of L. bulgaricus OLL1256 and S. thermophilus OLS3295. We conclude from these findings that yogurt fermented with L. bulgaricus OLL1073R-1, containing immunostimulative EPS, would have an immunomodulatory effect on the human body.

Cyclic oligomers of the repeating pentamer sequence of the elastic fiber, (Val1-Pro2-Gly3-Val4-Gly5)", were synthesized with = 1-6, and the cyclic oligomers were studied by means of proton and carbon-13 nuclear magnetic resonance, using methods which delineate polypeptide secondary structure. For each of the six cyclic peptides, the temperature dependences of peptide NH chemical shifts were determined in water (0 to 90 °C) and Me2SO (20 to 90 °C), the solvent dependences of peptide N/f chemical shifts were reported for a Me2SO -*• H2G solvent titration, and the solvent dependences of the peptide C-0 chemical shifts were determined for a Me2SO -» D20 solvent titration. These results were compared to those of the linear polypentapeptide in order to determine which cyclic structure would have a conformation most closely related to the conformation of the linear polymer. The conformations of the cyclopentapeptide and of the cyclodecapeptide were clearly different from that of the linear polypentapeptide, whereas those for = 3-6 were quite similar. In particular, the cyclopentadecapeptide ( = 3) and the cyclotricosapeptide (» = 6) were found to be excellent cyclic conformational correlates of the linear high polymer. These results were discussed relative to the pitch, number of residues per turn, and helix sense of the /3-spiral of the linear polypentapeptide.Tropoelastin, the soluble precursor protein of fibrous elastin,1,2 has been shown by Gray, Sandberg, and their colleagues3,4 to contain the related sequential polypeptides (Val ^Prc^-Gly 3-Gly4)", (Val1-Pro2-Gly3-Val4-Gly5)",and(Ala1-Pro2-Gly3-Val4-Gly5-Val6)".This laboratory has synthesized monomers, oligomers, and high polymers of these repeat sequences, has derived secondary structures for these repeats by using proton and carbon-13 nuclear magnetic resonance, and has proposed /3-spiral working models for the helical generation of the repeating conformational units.1 2345 In developing structures for a synthetic, voltage-dependent transmembrane channel, a concept of cyclic conformations with linear conformational correlates was derived.6 The concept states that, if there is a describable and relatively strain-free cyclic structure comprised of a substantial number of residues (preferably of a small number of repeat sequences), the process of breaking a single backbone bond and making only minor changes in torsion angles can convert the cyclic structure to a linear helical structure with approximately the number of residues in the cyclic structure becoming the number of residues per turn of helix.6 While this allows one to conceive of linear structures based on described cyclic structures, it can also be used experimentally in an inverse manner to determine if there are cyclic structures of repeat sequences which conformationally appear nealy identical with a linear sequential

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We have isolated, by hydroxyapatite chromatography with a non ionic detergent and a high salt concentration, a non‐glycosylated, membrane protein with a relative molecular weight of 34 kDa that had previously been found to be a major constituent of the membrane protein fraction showing ribosoine‐binding activity derived from rat liver rough microsomes (RM). The isolated 34 kDa protein (p34), when incorporated into a liposome model membrane, exhibited significant binding activity toward ribosomes, its binding properties being similar to those observed with intact R.M. immunochemical analyses using antibodies directed against p34 suggested that it is a membrane‐embedded RM surface protein, which is specifically localized in ribosome‐attached organelles and widely distributed among mammalian tissues. These results would constitute evidence that p34 is a likely candidate for an RM ribosome‐binding, protein.

Protein p34 is a non-glycosylated membrane protein characteristic of rough microsomes and is believed to play a role in the ribosome-membrane association. In the present study we isolated cDNA encoding p34 from a rat liver cDNA library and determined its complete amino acid sequence. p34 mRNA is 3.2 kb long and encodes a polypeptide of 307 amino acids with a molecular mass of about 34.9 kDa. Primary sequence analysis, coupled with biochemical studies on the topology, suggested that p34 is a type II signal-anchor protein; it is composed of a large cytoplasmic domain, a membrane-spanning segment and a 38-amino-acid-long luminally disposed C-terminus. The cytoplasmic domain of p34 has several noteworthy structural features, including a region of 4.5 tandem repeats of 23-24 amino acids. The repeated motif shows structural similarity to the leucine-rich repeat which is found in a variety of proteins widely distributed among eukaryotic cells and which potentially functions in mediating protein-protein interactions. The cytoplasmic domain also contains a characteristic hydrophilic region with abundant charged amino acids. These structural regions may be important for the observed ribosome-binding activity of the p34 protein.