Search

DNA sequencing shows that the intragenic duplication within the human haptoglobin Hp2allele was formed by a non-homologous, probably random, crossing-over within different introns of two Hp1genes, probably in an Hp1F/Hp1Sheterozygote.

The group-specific component (Gc) is a plasma protein that binds vitamin D. Recent characterization of human Gc cDNA demonstrated homology with serum albumin and α-fetoprotein. This study compares the sequences of the three proteins and demonstrates a strong evolutionary relationship. Albumin, α-fetoprotein and Gc evolved from an ancestral gene containing an intragenic triplication. Comparison of the amino acid sequences and patterns of double disulfide bonds suggests that the Gc gene may have diverged from an ancestral gene earlier in evolution than the genes encoding albumin and α-fetoprotein. Analysis of the amino acid and nucleotide sequences of the three internal domains of Gc revealed 19–23% amino acid sequence identity and the localization of three homology blocks with 40–44% nucleotide sequence identity. The deduced amino sequence of Gc furnished data for comparing its molecular configuration based on the predicted secondary structure with those predicted form human albumin and α-fetoprotein. Utilization of Gc cDNA has also led to the identification of its genomic DNA and detectioin of a human DNA polymorphism.