Invited review: Milk protein polymorphisms in cattle: Effect on animal breeding and human nutrition

Structural organization of the transcription units encoding the 6 main milk proteins. Caseins: α_s1-CN (CSN1S1), β-CN (CSN2), α_s2-CN (CSN1S2), and κ-CN (CSN3). Whey proteins: α-LA (LAA) and β-LG (LGB). A) Genomic organization of the bovine casein locus. B) Structural organization of the 6 milk protein transcription units. Open bars represent introns; exons are depicted by large, gray (5′ and 3′ untranslated regions), black (part of exon encoding the signal peptide), and colored (exons and part of exons encoding matured proteins) boxes. Size of exons is given, in base pairs, under each exon with its number indicated on the top (modified from Martin et al., 2002).

Alignment of the sequences of Bos taurus (BT), Capra hircus (CH), and Ovis aries (OA) casein genes (lines 1, 3, and 5) and preprotein (lines 2, 4, and 6). The positions above the first line refer to the protein, starting from the signal peptide (indicated as negative values) to the first AA of the mature protein (+01). Highlighted in yellow: nucleotides and AA differing in Capra hircus and/or Ovis aries with respect to Bos taurus; in blue: nucleotide and/or AA in which intraspecies genetic variations occur; in green: both interspecific and intraspecific variation occur; in gray: missing or conflicting data (AA 141–148 are not available in the ovine reference sequence; AA −9 is not clearly defined from the ovine nucleotide sequence; AA 137 is a controversial inversion with AA 138 in the bovine CSN2 sequence, see Table 2). Nucleotides affected by interspecific or intraspecific variation are bolded and in italics. CSN1S1=α_s1-CN gene; CSN1S2=α_s2-CN gene.

Alignment of the sequences of Bos taurus (BT), Capra hircus (CH), and Ovis aries (OA) casein genes (lines 1, 3, and 5) and preprotein (lines 2, 4, and 6). The positions above the first line refer to the protein, starting from the signal peptide (indicated as negative values) to the first AA of the mature protein (+01). Highlighted in yellow: nucleotides and AA differing in Capra hircus and/or Ovis aries with respect to Bos taurus; in blue: nucleotide and/or AA in which intraspecies genetic variations occur; in green: both interspecific and intraspecific variation occur; in gray: missing or conflicting data (AA 141–148 are not available in the ovine reference sequence; AA −9 is not clearly defined from the ovine nucleotide sequence; AA 137 is a controversial inversion with AA 138 in the bovine CSN2 sequence, see Table 2). Nucleotides affected by interspecific or intraspecific variation are bolded and in italics. CSN2=β-CN gene; CSN3=κ-CN gene.