Fig. 3. Structure-based sequence alignment of SCF with other short-chain helical cytokines of human species. Dots denote gaps. The secondary structure elements were assigned according to the output of the PROCHECK program (Laskowski et al., 1993) except the helix assignment for residues 35–38, which was identified by inspection of the hydrogen bond pattern. Secondary structures are shown in yellow with filled boxes referring to α-helices, half-filled boxes to 3₁₀-helices and arrows to β-strands. The solvent accessibility of the SCF dimer is indicated for each residue by an open circle if the fractional solvent accessibility is >0.4, a half-filled circle if it is 0.1–0.4, and a filled circle if it is <0.1. Residues at the SCF dimer interface are identified by stars, and the N-linked glycosylation sites by red Ys above the Asn residues.