The reovirus attachment protein, 1, is responsible for strain-specific patterns of viral tropism in the murine central nervous system and receptor binding on cultured cells. The 1 protein consists of a fibrous tail domain proximal to the virion surface and a virion-distal globular head domain. To better understand mechanisms of reovirus attachment to cells, we conducted studies to identify the region of 1 that binds cell surface carbohydrate. Chimeric and truncated 1 proteins derived from prototype reovirus strains type 1 Lang (T1L) and type 3 Dearing (T3D) were expressed in insect cells by using a baculovirus vector. Assessment of expressed protein susceptibility to proteolytic cleavage, binding to anti-1 antibodies, and oligomerization indicates that the chimeric and truncated 1 proteins are properly folded. To assess carbohydrate binding, recombinant 1 proteins were tested for the capacity to agglutinate mammalian erythrocytes and to bind sialic acid presented on glycophorin, the cell surface molecule bound by type 3 reovirus on human erythrocytes. Using a panel of two wild-type and ten chimeric and truncated 1 proteins, the sialic acid-binding domain of type 3 1 was mapped to a region of sequence proposed to form the more amino terminal of two predicted ␤-sheet structures in the tail. This unit corresponds to morphologic region T(iii) observed in computer-processed electron micrographs of 1 protein purified from virions. In contrast, the homologous region of T1L 1 sequence was not implicated in carbohydrate binding; rather, sequences in the distal portion of the tail known as the neck were required.Results of these studies demonstrate that a functional receptor-binding domain, which uses sialic acid as its ligand, is contained within morphologic region T(iii) of the type 3 1 tail. Furthermore, our findings indicate that T1L and T3D 1 proteins contain different arrangements of receptor-binding domains.

Grassland birds have experienced steeper population declines between 1966 and 2015 than any other bird group on the North American continent, and migratory grassland birds may face threats in all stages of their annual cycle. The grassland‐associated long‐billed curlew (Numenius americanus) is experiencing population declines in regional and local portions of their North American breeding range. The nesting period is an important portion of the annual cycle when curlews may face demographic rate limitations from a suite of threats including predators and anthropogenic disturbance. We compared nest sites to random sites within breeding territories to examine nest site selection, and modeled correlates of nesting success for 128 curlew nests at 5 Intermountain West sites. Nest sites were 6 times more likely than random sites to be situated adjacent to existing cowpies. Additionally, curlews selected nest sites with shorter vegetation, and less bare ground, grass, and shrub cover than at random sites within their territories. Nest success varied widely among sites and ranged from 12% to 40% in a season with a mean of 27% for all nests during the 2015 and 2016 seasons. Higher nest success probability was associated with higher curlew densities in the area, greater percent cover of conspicuous objects (cowpies, rocks) near the nest, and higher densities of black‐billed magpies (Pica hudsonia) and American crows (Corvus brachyrhynchos) at the site. We also found increased probability of nesting success with increased distance from a nest to the nearest potential perch in that territory. Given the central role of working lands to curlews in much of the Intermountain West, understanding limitations to nesting success in these diverse landscapes is necessary to guide adaptive management strategies in increasingly human‐modified habitats. We suggest some grazing and irrigation practices already provide suitable nesting conditions for curlews, and others may require only minor temporal shifts to improve compatibility. © 2019 The Wildlife Society.

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