Abstract
The keratin-associated proteins (KAPs) are fundamental components of hair and wool fibres, and are believed to in part be responsible for some of the properties of these fibres. KAPs can be divided into three groups: the high sulphur (HS) KAPs, the ultra-high sulphur (UHS) KAPs and the high glycine-tyrosine (HGT) KAPs. KAP8 is a HGT-KAP family and was believed to be coded for by a single gene in both humans and sheep. However, the recent identification of a KAP8-2 gene in goats led us to investigate whether a KAP8-2 gene exists in sheep.A BLAST search of the Ovine Genome Assembly v2.0 using the coding sequence of caprine KRTAP8-2 identified a homologous region on sheep chromosome 1 (OAR1:123005473_123005664; E = e-101). This region was clustered with a number of previously identified KAP genes including (in order from the centromere) KRTAP11-1, KRTAP7-1, KRTAP8-1, KRTAP6-2, KRTAP6-1, KRTAP13-3 and KRTAP24-1. PCR-SSCP analysis of the notional gene revealed two dissimilar PCR-SSCP banding patterns, representing two DNA sequences. A single nucleotide difference 21 bp upstream of the TATA box was identified. The two sequences did not have great homology with known ovine KRTAP sequences, but high sequence identity was found with KRTAP8-2 from goats and reindeer. These results suggest that sheep possess a KAP8-2 gene and that this gene is polymorphic.The notional KAP8-2 protein is comprised of 63 amino acid residues and is rich in glycine and tyrosine, but has a low cysteine content. In contrast to other HGT-KAPs, ovine KAP8-2 contains more acidic amino acid residues, and this would likely result in a lower isoelectric point (pI) of 6.3.Electronic supplementary materialThe online version of this article (doi:10.1186/2193-1801-3-528) contains supplementary material, which is available to authorized users.
Highlights
The keratin-associated proteins (KAPs) are part of the matrix of wool fibres and form a cross-linked network with the keratin intermediate filaments (Powell & Rogers 1997)
This study has identified a new gene encoding a high glycine-tyrosine (HGT)-KAP in sheep
The gene was grouped with other KAP genes on ovine chromosome 1, but located at a different position and with a lower sequence similarity to these genes
Summary
The keratin-associated proteins (KAPs) are part of the matrix of wool fibres and form a cross-linked network with the keratin intermediate filaments (Powell & Rogers 1997). They typically possess a high content of either cysteine, or glycine and tyrosine. In a Merino half-sib family, this chromosome region has been suggested to be associated with variation in wool fibre diameter (Parsons et al 1994)
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