Identification And Its Genetical Characteristics Of Caprine KRTAP20-2 And KRTAP26-1 Genes

Keratin-associated proteins(KAPs)are main structural components of wool fiber and cashmere,which influencing the physical and chemical property of the latter.High glycine/tyrosine KRTAP20-2 and High sulfur KRTAP26-1 genes have been described and reported in human beings and Musmusculus,but never identified in goat.The coding regions of human KRTAP20-2 and KRTAP26-1 were used as model sequence,BLAST software was employed to detect the high homology sequence of human KRTAP20-2 and KRTAP26-1 genes with the one of goats in this study,which was presumed the caprine KRTAP20-2 and KRTAP26-1 genes.PCR-SSCP analysis revealed that the putative gene PCR amplification length was 275 bp,and there were three different nucleotide sequences(named as A,B,and C,respectively)were detected in 605 individuals from five goat populations.The results of sequence homology and phylogenetic tree showed that these three sequences have low homology with the identified goat KRTAPs,but have the highest homology with the KRTAP20-2 genes of human beings and Musmusculus.This suggested that these four sequences identified may stand for four different alleles of caprine KRTAP20-2 gene.Six single nucleotide polymorphisms(SNPs)were discovered from these alleles and four SNPs were non-synonymous substitutions,which would result in the change of amino acid sequences accordingly.The caprine KAP20-2,which has high percentage of Glycine(37.81mol%)and Tyrosine(25.81-37.81mol%)and moderate percentage of Cysteine(12.90mol%)and no six amino acids,such as Alanine,and et al,was composed of 62 amino acids 5-6 phosphorylation sites were detected from three polypeptide chains,and there were no glycosylation site.The molecular weight of caprine KAP20-2 protein is only 6.6 k Da,which belongs to the stable water soluble protein.The secondary structure of protein is composed of 4 common substructures.Polymorphic information content(PIC)showed that KRTAP20-2 gene in five goat populations has a moderate polymorphism,but allelic frequencies exists difference among different populations.It was drawn a conclusion that caprine KRTAP20-2 gene has an abundant nucleotide substitution,and the substitutions identified in goat may have an effect on cashmere production.The putative KRTAP26-1gene PCR amplification length was 626 bp,and there were four different nucleotide sequences(named as A,B,C,and D,respectively)were detected in 605 individuals from five goat populations.The results of sequence homology and phylogenetic tree showed that these four sequences have low homology with the identified goat KRTAPs,but have the highest homology with the KRTAP26-1 gene of human beings,Canis lupus familiaris,Musmusculus and Rattusnorvegicus.This suggested that these four sequences identified may stand for four different alleles of caprine KRTAP26-1 gene.Six single nucleotide polymorphisms(SNPs)were discovered from these alleles and three SNPs were non-synonymous substitutions,which would result in the change of amino acid sequences accordingly.The caprine KAP26-1,which has high percentage of Serine(21.74-22.83mol%)and moderate percentage of Proline(11.96mol%)and Leucine(9.24%-9.78mol%),was composed of 184 amino acids.36-38 phosphorylation sites and 12-13 glycosylation sites were detected from four polypeptide chains.Because of so many protein glycosylation and phosphorylation sites,it may affect on cashmere production.Polymorphic information content(PIC)showed that KRTAP26-1 gene in five goat populations have an moderate polymorphism.There exists difference among four allelic frequencies.Allele A,B and D were detected from five goat populations,but allele C was not detected in Zhongwei goat.It was drawn a conclusion that caprine KRTAP26-1 gene has an abundant nucleotide substitution,and the substitutions identified in goat may have an effect on cashmere production.