The Sem1 protein. (A) Polyclonal antibodies to Sem1p recognize a 12-kDa protein in wt cells. This protein is absent in sem1-Δ1 and present in increased amounts in SEM1-overexpressing cells. (B) Cell fractionation of NY1427. Sem1p is mainly soluble but also is found associated with the 100,000 × g pellet in wt cells. WT, total-cell lysate prepared from NY1427; Δ, total-cell lysate from H1286 (sem1-Δ1). (C) A majority of Sem1p is removed from the pellet material by 1 M KCl, 2.5 M urea, or 1% (wt/vol) Triton X-100 in 10 mM Hepes (pH 7.2). Roughly 50% of Sem1p can be extracted from the 100,000 × g pellet with 10 mM Hepes (pH 7.2) alone.