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The intracellular sites of biosynthesis of the structural proteins of murine hepatitis virus A59 have been analyzed using cell fractionation techniques. The nucleocapsid protein N is synthesized on free polysomes, whereas the envelope glycoproteins E1 and E2 are translated on the rough endoplasmic reticulum (RER). Glycoprotein E2 present in the RER contains N‐glycosidically linked oligosaccharides of the mannose‐rich type, supporting the concept that glycosylation of this protein is initiated at the co‐translational level. In contrast, O‐glycosylation of E1 occurs after transfer of the protein to smooth intracellular membranes. Monensin does not interfere with virus budding from the membranes of the endoplasmic reticulum, but it inhibits virus release and fusion of infected cells. The oligosaccharide side chains of E2 obtained under these conditions are resistant to endoglycosidase H and lack fucose suggesting that transport of this glycoprotein is inhibited between the trans Golgi cisternae and the cell surface. Glycoprotein E1 synthesized in the presence of monensin is completely carbohydrate‐free. This observation suggests that the intracellular transport of this glycoprotein is also blocked by monensin.

The effect of barley germination and kilning on three putative beer foam-positive proteins was investigated by immunoblotting and ELISA procedures. These procedures involved the use of specific antibodies raised to purified lipid transfer protein 1 (LTPl)and the two protein Zforms, Z4 (BSZ4) and Z7 (BSZ7). The free fraction ofBSZ4 and BSZ7, and all LTP1 were extracted by aqueous salt-solution from barley and malt. The addition of reducing agent allowed the extraction of bound BSZ4 and BSZ7. A previously undescribed fraction of BSZ4 and BSZ7, refered to as latent, was extracted with SDS and reducing agent. The barley combined fraction (free + bound fractions) was surveyed in 93 barley varieties to show that BSZ4 was the dominant isoform, on average constituting "80 % of all protein Z. Considerable variation was observed between varieties in the level of LTP1 (502-1144 fig/g) and the combined fractions of BSZ4 (18-2136 fig/g) and BSZ7 (38-771 pg/g). The free fraction is expected to be more available for extraction into wort during mashing than the bound or latentfractions. The level ofLTPl did not change substantially during germination, but a significant proportion of the latent and/or bound protein Z fractions was converted into the free fraction. In the seven varieties studied the free fraction of BSZ4 and BSZ7 increased 149-300% and 49-141%, respectively. Proteolytic cleavage in the reactive site loop converts protein Z to heat-and protease-stable forms that survive the brewing process. During germination most of the free BSZ4 and 30-70% BSZ7 was converted to the cleaved form. Kilning was found to reduce the amount of protein Z and LTP1 that could be extracted by 10-30% and 7-37%, respectively, which is likely to be counter productiveforfoam quality. These results suggest that barley variety selection and optimisation of germination and kilning protocols during malting may be opportunities for improvement of beer foam quality.

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