Enhancement of Protein Secretion in Saccharomyces cerevisiae by Overproduction of Sso Protein,a Late-acting Component of the Secretory Machinery

Increased production of secreted proteins in Saccharomyces cerevisiae was achieved by overexpressing the yeast syntaxins, Sso1 or Sso2 protein, the t-SNAREs functioning at the targeting/fusion of the Golgi-derived secretory vesicles to the plasma membrane. Up to four- or six-fold yields of a heterologous secreted protein, Bacillus α-amylase, or an endogenous secreted protein, invertase, were obtained respectively when expressing either one of the SSO genes, SSO1 or SSO2, from the ADH1 promoter on a multicopy plasmid. Direct correlation between the Sso protein level and the amount of secreted α-amylase was demonstrated by modulating the expression level of the SSO2 gene. Quantitation of the α-amylase activity in the culture medium, periplasmic space and cytoplasm suggests that secretion into the periplasmic space is the primary stage at which the SSO genes exert the secretion-enhancing function. Pulse-chase data also support enhanced secretion efficiency obtained by SSO overexpression. Our data suggest that the Sso proteins may be rate-limiting components of the protein secretion machinery at the exocytosis step in yeast. © 1997 John Wiley & Sons, Ltd.     

DESIGNING HOPE: RATIONALES OF MIXED‐INCOME HOUSING POLICY

Rationales used to legitimize forced dispersal and mixed‐income housing policies are socially constructed based on assumptions about concentrated poverty. This study evaluates qualitative data on public housing residents who were in the process of being dispersed as part of a HOPE VI program in order to examine their thoughts about their original home and neighborhood. Residents’ thoughts about their neighborhood are compared to policy rationales. Results indicate that current policy rationales are mostly in line with the goals and motivation of the city but are largely incongruent with the perceptions residents have of their pre‐relocation home and neighborhood. The article concludes with policy recommendations for increasing and incorporating residents’ views into policy design.     

INTRODUCTION: COMPARATIVE CIVIC CULTURE

ABSTRACT: This symposium presents a subset of findings from a larger multicity research project using a single operational and methodological scheme to explore the nature of civic culture. The overall purpose is to explore civic cultures in an array of larger cities, test an initial typology of civic culture, and begin to examine the connections between civic culture and local policy. The articles in the symposium make clear that it is possible to empirically identify a parsimonious taxonomy of local civic cultures focusing on systems of community power, values, and decision‐making. While many questions about the internal dynamics of each type remain to be answered, the civic cultures identified here appear empirically distinct and theoretically logical. Future research and dialogue need to focus on defining what culture is and what it is not, and then move to explore the linkages between the elements of civic culture and ultimately to local policy.     

MACRODONTIN, A NEW PROTEASE ISOLATED FROM FRUITS OF PSEUDANANAS MACRODONTES (MORR.) HARMS (BROMELIACEAE)

A cysteine proteinase was isolated from immature fruits of Pseudananas macrodontes (Morr.) Harms, a species taxonomically close to pineapple grown in the northeast of Argentina. The protease is active at pH 7.0 to 10.5, and rather unstable at temperatures over 45C. Crude extracts were purified by acetone fractionation followed by chromatofocusing at the pH range 4.5 to 6.5. Two main proteolytic fractions were obtained: fraction I (M_r= 20.6 kDa, pI = 5.9) and fraction II (M_r= 19.3 kDa, pI = 5.3), both homogeneous by gel-filtration and SDS-PAGE criteria. This new plant protease (“macrodontin”) could be valuable in processes carried out in neutral-weak alkaline media. The thermal behavior of the crude enzyme is also a useful property, since it could be easily inactivated in foodstuffs by heating 10 min at 75C. Comparison of macrodontin and alcalase proteolytic behavior on soy concentrates is presented.     

Inhibition of Lactic Acid Bacteria by Herbs

Increasing concentrations (0.5–8g/liter) of oregano, rosemary, sage, and thyme progressively delayed growth and acid production by Lactobacillus plantarum and Pediococcus acidilactici in a liquid medium. After the bacteriostatic activity was overcome, all four herbs strongly stimulated acid production. The relative inhibitory effect of the herbs toward both microorganisms was oregano ? rosemary = sage gt; thyme. L. plantarum was more resistant than P. acidilactici to the toxic effect of the herbs. Organisms from cultures exhibiting delayed fermentation in the presence of sublethal concentrations of an herb, when subcultured into fresh media containing identical herb concentrations, initiated fermentation without delay, indicating development of resistance to the herb's effect. Moreover, bacteria which had acquired a resistance to one herb were also resistant to the other three herbs.     

Loss of urea from the flesh of ray (Raja radiata) during the canning process

Elasmobranch fish are under-utilized as food because the high urea content produces unpleasant odours and flavours on storage and cooking. Cooking frozen ray (Raja radiata) in water or in steam, followed by canning in brine reduced the urea content of the muscle 4–5-fold. This should reduce off-flavour and thus improve utilization of ray as a canned product.     

COOKING EFFECTS ON TITIN IN FRESH AND PROCESSED BEEF PRODUCTS

Fresh bovine longissimus thoracis muscle samples, heated at 73C for 0, 5, 15, 30, 45, 60, 90 and 120 min, were subjected to sodium dodecyl sulfate polyacrylamide gel electrophoresis and western blot analysis. Titin was both aggregated into large protein masses and degraded into smaller fragments (two apparently independent processes) in fresh muscle samples heated 15 min or more at 73C. Samples removed at various points during the manufacture of a tumbled cured beef product were also subjected to electrophoresis and western blot analysis. Titin was primarily degraded into smaller polypeptide fragments during the manufacture of this product with no large titin aggregates observed. Commercially manufactured meat products, when examined by these techniques, contained both titin aggregates and degradation products. These results suggest that titin can be aggregated into large protein masses and degraded into smaller polypeptide fragments during the heating of fresh or processed meat products.