Comparison of the primary and tertiary structures of the NiV, HeV, MeV, RPV, PPRV, CDV, PDV, SeV, HPIV-1, HPIV-3, SV5, and NDV paramyxovirus F proteins. The 3-D structure of each paramyxovirus F protein was modeled based on the solved crystal structure of the HPIV-3 F protein (see Materials and Methods), and the N-linked glycosylation sites were mapped onto the predicted structure. (A) Linear comparison of the 12 sequences based on Clustal W multiple sequence alignments. The amino acid positions (not to scale) of the potential N-linked glycosylation sites in NiV-F are shown in red in the top sequence representation. Actual glycan attachment sites are indicated by a branched tree symbol at the amino acid position. Positions of the other paramyxovirus F proteins are shown below the NiV-F sequence, with the amino acid sequence position indicated to the left of the glycan symbol and its position in the predicted 3-D structure on the right; circles, triangles, and diamonds represent glycans located in the head, neck, and stalk region, respectively, of the predicted or actual (for HPIV3) 3-D structure. Asterisks denote N-linked glycosylation sites that could not be structurally mapped. (B) Carbon backbone representation of the HPIV-3 F structure (), representing the general overall fold of the paramyxovirus F protein. N-linked glycosylation sites which can be mapped onto this structure using the threading methodology described in Materials and Methods are indicated by circles; see the key in the figure. The heptad repeat regions (HR-A, HR-B, and HR-C) and head, neck, and stalk regions are also indicated.