Nucleotide sequence divergence and functional constraint in VIP precursor mRNA evolution between human and rat.

The nucleotide sequence analysis of cloned cDNA for VIP precursor from rat cerebral cortex reveals that the precursor contains both rat VIP and PHI-27. The deduced primary structure of rat VIP is identical with human VIP. The amino acid sequence of rat PHI-27 differs by 4 amino acids from human PHM-27. When each VIP precursor is divided functionally into 6 domains, the amino acid sequence homology between rat and human precursors ranges from 69 to 100%. In contrast, any domain exhibits an essentially equal degree of nucleotide sequence homology.