Identification of the ovine KAP11-1 gene (KRTAP11-1) and genetic variation in its coding sequence

Keratin-associated proteins (KAPs) are a structural component of the wool fibre and form the matrix between the keratin intermediate filaments (KIFs). The gene encoding high sulphur-protein KAP11-1 has been identified in human, cattle and mouse, but not yet in sheep, despite the economic importance of wool. In this study, PCR using primers based on the cattle KAP11-1 gene sequence produced an amplicon of the expected size with sheep DNA. Upon using PCR-Single Stranded Conformational Polymorphism (PCR-SSCP) analysis in 260 sheep, six different PCR-SSCP patterns were detected. Either one or a combination of two banding patterns was observed for each sheep, suggesting they were either homozygous or heterozygous for this gene. Sequencing of the amplicons confirmed the occurrence of six DNA sequences. All of these were unique, and the greatest homology was with KRTAP11-1 sequences from cattle, human and mouse, suggesting that they were derived from the ovine KAP11-1 gene and were allelic variants. The ovine KAP11-1 gene had an open reading frame of 477 nucleotides encoding 159 amino acids. The putative protein was rich in serine, cysteine, and threonine which account for 18.2-18.9, 12.6 and 12.0 mol%, respectively. Of these, approximately 20 of the serine and threonine residues might be phosphorylated. Five nucleotide substitutions were identified, and one was non-synonymous and would result in an amino acid change at a potential phosphorylation site. The genetic variation found in KRTAP11-1 may influence its expression, protein structure, and/or post-translational modifications, and consequently affect wool fibre structure and wool traits.