Recombinant single domain antibody fragments (VHHs) that derive from the unusual camelid heavy chain only IgG class (HCAbs) have many favourable properties compared with single-chain antibodies prepared from conventional IgG. As a result, VHHs have become widely used as binding reagents and are beginning to show potential as therapeutic agents. To date, the source of VHH genetic material has been camels and llamas despite their large size and limited availability. Here we demonstrate that the smaller, more tractable and widely available alpaca is an excellent source of VHH coding DNA. Alpaca sera IgG consists of about 50% HCAbs, mostly of the short-hinge variety. Sequencing of DNA encoding more than 50 random VHH and hinge domains permitted the design of PCR primers that will amplify virtually all alpaca VHH coding DNAs for phage display library construction. Alpacas were immunized with ovine tumour necrosis factor alpha (TNFalpha) and a VHH phage display library was prepared from a lymph node that drains the sites of immunizations and successfully employed in the isolation of VHHs that bind and neutralize ovine TNFalpha.

The rotavirus non‐structural glycoprotein (NS28), the receptor for the virus core during budding into the lumen of the rough endoplasmic reticulum (RER), is 175 amino acids long and possesses an uncleaved signal sequence and two amino‐terminal glycosylation sites. Utilizing one of three potential hydrophobic domains, the protein spans the membrane only once, with the glycosylated amino‐terminal region oriented to the luminal side of the ER and the carboxy‐terminal region to the cytoplasmic side. To localize sequences involved in translocation of NS28, we constructed a series of mutations in the coding regions for the hydrophobic domains of the protein. Mutant protein products were studied by in vitro translation and by transfection in vivo. In transfected cells, all mutant forms localize to the ER, and none are secreted. In vitro, each of the three hydrophobic domains is able to associate with microsomes. However, glycosylation and proteolysis of wild‐type and mutant forms of NS28 indicates that the wild‐type protein is anchored in the membrane only by the second hydrophobic domain, leaving approximately 131 residues exposed on the cytoplasmic side for receptor ‐ ligand interaction.

We developed a procedure for automated confocal microscopy to image the effect of the non-essential yeast gene deletion set on the localisation of the plasma membrane GFP-labelled protein Mrh1p-GFP. To achieve this it was necessary to devise an expression system expressing Redstar2 RFP-fluorescence specifically in the nucleus, mCherry RFP at a lower intensity in the cytoplasm and Mrh1p-GFP in the plasma membrane. This fluorescence labelling scheme utilising specifically designed image analysis scripts allowed automated segmentation of the cells into sub-regions comprising nuclei, cytoplasm and cell-surface. From this high-throughput high content screening approach we were able to determine that gene deletions including emc1Δ, emc2Δ, emc3Δ, emc4Δ, emc5Δ and emc6Δ, caused intracellular mislocalisation at the ER of a plasma membrane protein Mrh1p-GFP. CPY processing patterns were unaffected in these mutants and collectively our data suggest a transport role for the EMC genes within the early secretory pathway. HAC1 is central to the unfolded protein response (UPR) and in its absence, i.e. the absence of UPR, emc1Δ-, emc3Δ-, emc4Δ-, emc5Δ-hac1Δ double mutants were specifically hypersensitive to ER-stress (tunicamycin) lending credence to the usefulness of the high content microscope screening for discovery of functional effects of single mutants.

. Maturation of rotavirus occurs in the ER.The virus transiently acquires an ER-derived membrane surrounding the virus particle before the eventual formation of double-shelled particles . The maturation process includes the retention and selective loss of specific viral protein(s) as well as the ER-derived membrane during formation of the outer capsid of the mature virus. When infected cells were depleted of Ca++ by use of the ionophore A23187 in calcium-free medium, membrane-enveloped intermediates were seen to accumulate. When Mn++, an efficient Ca++ competitor, was used to replace Ca++ in the medium, the accumulation of the enveloped intermediate was again observed, pointing to an absolute requirement of Ca++ in the maturation process. It was previously demonstrated in this laboratory that a hetero-oligomeric complex of NS28, VP7, and VP4 exists which may participate in the budding of the single-shelled particle R TAVIRUs, a double capsid virus whose maturation process involves the ER (1,7,8,10,24), has provided a unique system in which to examine the posttranslational processing, targeting, and ER retention of both its nonstructural and structural glycoproteins, NS28 and VP7, respectively. Other studies have investigated the role of calcium in virus assembly (18,22,23), in the association of proteins within the ER (20), in the perturbation of egress of secretory proteins (13), and in the retention of soluble ERtargeted proteins to this organelle (6) . It appears that the presence of cations and glycosylation plays a significant role in the association of proteins, possibly through conformational, energetic, or, in the case of the presence of cations, enzymatic mechanisms.During maturation, rotavirus cores form in the viroplasm and acquire the inner capsid proteins to form single-shelled particles . NS28 is a transmembrane glycoprotein (2, 5) that modifies the ER and is the receptor for the subsequent budding of these single-shelled particles into the ER (3, 15) as the transient membrane-enveloped particle is formed . This into the ER (Maass, D. R., and P H. Atkinson. 1990. J. Virol. 64 :2632-2641) . The present study demonstrates that either in the absence of Ca++ or in the presence of tunicamycin, a glycosylation inhibitor, VP7 is excluded from these hetero-oligomers . In the presence of Mn", VP4 was blocked in forming a hetero-oligomeric complex with NS28 and VP7. The electrophoretic mobility of the viral glycoproteins synthesized in the presence of the ionophore were found to be altered. This size difference was attributed to altered N-linked glycosylation and carbohydrate processing of the viral glycoproteins . These results imply a major role for calcium and the state of glycosylation of NS28 in the assembly and acquisition of specific viral protein conformations necessary for the correct association of proteins during virus maturation in the ER. intermediate membrane-enveloped particle has been isolated (16a) and comprises, in addition to the structural proteins of the virus, the nonstructural...

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