Antitrypsin Related Protein (ATR)

The nucleotide sequence of the ATR gene showed extensive homology with the authentic AAT gene in the introns as well as exons. The conservation of all RNA splice sites and lack of internal termination codons in the exons suggested that it may not be a classic pseudogene. If expressed, it would result in a protein of 420 amino acid residues, exhibiting a 70% overall homology with AAT. The signal peptide sequence was well conserved, but the active site of protease inhibition (met-ser) in AAT had been changed to trp-ser. The findings suggested that the putative protein is a secretory serine protease inhibitor with an altered substrate specificity. Since even the introns showed 65% nucleotide sequence homology with the authentic AAT gene, ATR appears to have been derived from a recent duplication of the AAT gene.