Structure and expression of rat and mouse mRNAs for Zn-alpha 2-glycoprotein

Rat and mouse cDNAs for Zn-alpha 2-glycoprotein (Zn alpha 2gp) were isolated from liver libraries (lambda gt11) and compared with the human one. The lengths of cDNA inserts analyzed were 1,233 and 1,273 nucleotides for rat and mouse, respectively. The deduced amino acid sequences suggested that rat and mouse Zn alpha 2gp proteins consist of 279 and 290 amino acid residues in the mature form, respectively. They have 59.4% (rat) and 58.6% (mouse) identities in amino acid sequence with the human counterpart, and between rat and mouse the identity is 88.5%. Among the three domains, domain B is best conserved; the identities are 74.7, 73.6, and 95.6% between human and rat, human and mouse, and rat and mouse, respectively. Four cysteine and eight tryptophan residues are all conserved, and two of the three asparagine residues that carry a glycan in the human protein are conserved. Analysis of rat tissues by Northern blot suggested that its mRNA is expressed in liver, and, to a much lesser extent in submandibular gland, lung, kidney, and stomach. A more detailed study by in situ hybridization demonstrated that some epithelial cells of renal tubules and the isthmus and the neck zone cells of gastric fundic glands express Zn alpha 2gp mRNA.