Figure 1

HP alleles and protein structures. (a) HP1 and HP2 allele structure; HP1 allele contains 5 exons, while HP2 is made up of 7 exons: exons 1 to 4 correspond to HP1, exons 5 and 6 is the duplication of exon 3 and 4, and exon 7 corresponds to exon 5 in HP1. (b) HP isoform and protein structure. HP1 allele encode for alpha-1 and beta chain (in blue and orange, respectively), while HP2 allele for alpha-2 and beta chain (green and orange respectively). The quaternary structures of HP genotypes are also illustrated (modified from¹⁷). (c) HP gene encode for signal peptide, from amino-acid residues 1–18, and mature protein sequence from 19 to 347 or 406, depending on the allele of origin: HP1 allele encoding for alpha-1 chain (residues 19–101) and beta chain (d), HP2 allele for alpha-2 chain (residues 19–160) and beta chain (e). Alpha-1 chain lacks of residues 29–87 of alpha-2 chain, and beta chain is common to HP1 and HP2 alleles.