Analysis of cloned zebrafish β4.1 and β4.2 subunit genes. Presentation and labeling as in Figure 1. A) Alignment of cloned human, rat, and zebrafish β4 amino acid sequences. S- = conserved cysteine in β4 that is a putative site of covalent linkage with a partner α subunit; N = predicted N-linked glycosylation site (N1 = human, N2 = rat, N3 = zebrafish β4.1, N4 = zebrafish β4.2); M = site of putative Long QT syndrome-causing mutation L179F; S1 = nonsynonymous Hsβ4 SNP (A/C > N210H). B) Genomic organization of zβ4.1 and zβ4.2 derived from comparing cloned cDNA sequences with genomic sequences of zebrafish chromosomes 15 and 5, respectively. zβ4.1 has five exons and zβ4.2 has six exons. C) All zβ4.1 and zβ4.2 splice sites exhibit consensus GT-AG donor/acceptor sequences. D) Schematic diagram of zβ4.1 and zβ4.2 proteins.