Figure 2

Schematic representation of the exon/intron organization of VCBP genes. VCBPs belong to five subgroups, each gene encodes three domains; a pair of V-LIKE DOMAIN [3], designated as [D1] and [D2] V domains, and a C-terminal chitin-binding domain (CBD). VCBP2 and VCBP5 are related closely and share the same overall exon/intron organization; the other VCBPs are more distantly related. A hyper-polymorphic region is localized to the second exon (EX2, shaded) encoding the N-terminal region of the [D1] V domain of VCBP2 and VCBP5. Additional polymorphisms have been noted (not shown) in various exons among different VCBP subgroup alleles. Exon and intron sizes are to scale or marked by (//). Lengths in nucleotides are indicated directly below exons and introns. Secretion signals are encoded by EX1. Termination exons end in (*). All VCBP exons utilize splicing frame 0 (sf0) (Aide-memoire, Splicing sites, http://www.imgt.org/), see Additional file 1: Table S1. One representative allele was chosen for illustration purposes, and selected if the same exon/intron characteristics were observed in at least two other alleles; alleles are: VCBP5S1*02, VCBP4S1*02, VCBP1S1*02, and VCBP3S1*02, respectively (see Additional file 1: Table S1). VCBP3 alleles possess additional, distantly related CBD-encoding ORFs (grey boxes). Some of these appear to have splice signals and one version represents an out-of-frame splice variant. A similar sequence was recovered from the transcription products of PAC 30b18 expression in a 293T transfection assay (see text). Variation in exon sizes and extensive variation in introns exists across most alleles and is noted (see text). Domains [D] are specified as: white diamond = [D1] V, white triangle = [D2] V and white star = [D3] CBD; stop codons are indicated by (*).