The predicted peptide structures of the V, V/C2, TM, Cyt1, and
Cyt2 of the 24 NITR genes encoded in PAC 19B20; pseudogenes 6 and 8 are
not included. Genes are listed in an order that facilitates intergenic
comparisons; vertical brackets in V and V/C2 enclose the 10
members of the SN6A type-1 gene family. ▵, Uncertainties
with regard to the mature start site of NITR genes, referenced to gene
10; alternative start sites are predicted, as described (18). The basis
for the designation of V and V/C2 domains in exon II is based
largely on the homologous relationship of the NITR genes to Ig and TCR
V domains (Fig. 1b), the shorter lengths of V/C2
domains and the relative locations of V/C2 exon/intron
boundaries (▴) in two other species of bony fish, in which
an intron separates the (two) extracellular Ig domains. The outlier
genes (5, 9, and 10) are separated. Note the interspersed color bands
and extensive regions of nonidentity in the three designated outliers,
particularly in V/C2. For reference purposes, positions that are
(highly) conserved between VH, Vκ,
Vλ, TCRVα, and
TCRVβ are designated in one-letter code by using
International Immunogenetics Database (IMGT) numbering (Fig.
1b legend); conserved cysteine is circled. The location
(by reference to Ig/TCR designations) of sequence regions
corresponding to CDR1 and CDR2 as well as the boundaries of the glycine
bulge (J homology) regions, [(F)GXG], are shown by brackets above and
below the alignments. Absolute identity is shown in red (up to one
difference is allowed); substitutions that result in changes which
retain functional groups, defined conservatively as: G or A; I, L, M,
or V; K or R; S or T; F or Y; D or E; and N or Q, are shown in yellow.
Recognized TM and Cyt1 families are designated by Roman numerals to the
left of the alignments. ITIMs in Cyt2 are enclosed. Variation among the
members of the SN6A type-1 gene family (enclosed in a vertical bracket)
are shown in the continuous horizontal color bars below gene 26.
Positions at which no variation occurs are shown in red; a single amino
acid difference in one family member is shown in pink; one amino acid
substitution in two or more family members is shown in orange; two or
more different substitutions in multiple family members are shown in
blue. The comparison is referenced to the predicted start site of gene
10.