Tracking the evolution of the proenkephalin gene in tetrapods.
ABSTRACT In gnathostomes there is remarkable consistency in the organization of the proenkephalin gene. This opioid precursor encodes seven opioid (YGGF) sequences: five pentapeptide sequences, a met-enkephalin-7 sequence and a met-enkephalin-8 sequence. Yet, within vertebrate lineages there can be distinct sets of pentapeptide opioids (YGGFM or YGGFL). In the Sarcopterygii, the sixth opioid position in lungfishes and anuran amphibian proenkephalin genes encodes a met-enkephalin (YGGFM) sequence. However, in mammalian proenkephalin there is a leu-enkephalin (YGGFL) sequence at this position. This study was done to test the hypothesis that the presence of the leu-enkephalin sequence in mammals is a feature common to amniote vertebrates, but not present in anamniote vertebrates. To resolve this issue, proenkephalin cDNAs were cloned from the urodele amphibians, Amphiuma means and Necturus maculosus, and two amniote vertebrates, the turtle, Chrysemys scripta, and the brown snake, Storeria dekayi. As predicted, a met-enkephalin sequence is present at the sixth opioid position in urodele amphibians; whereas, a leu-enkephalin sequence is present at this opioid site in the reptile proenkephalin sequences. These data are consistent with the conclusion that the transition from a met-enkephalin sequence to a leu-enkephalin sequence at the sixth opioid position in tetrapod proenkephalins occurred in the ancestral proto-reptiles. Phylogenetic analyses, using the Maximum Parsimony and Neighbor-Joining algorithms, of the amphibian proenkephalin sequences supported the position that anuran and urodele amphibians are a monophyletic assemblage. The same analysis of reptile-related proenkephalin sequences, including the deduced amino acid sequence of a partially characterized alligator proenkephalin cDNA, could not conclusively resolve the phylogeny of the major reptilian orders.
- SourceAvailable from: Sadao Kimura[show abstract] [hide abstract]
ABSTRACT: A 3200-dalton adrenal enkephalin-containing peptide, designated peptide E, that exhibits high opiate activity in the guinea pig ileum longitudinal muscle preparation was purified, and its structure was determined. It contains an amino-terminal [Met]enkephalin sequence and a [Leu]enkephalin sequence at the carboxyl terminus. Sequence analysis revealed that peptide E arises from a previously characterized 4900-dalton adrenal enkephalin-containing peptide. Peptide E was shown to be 30 times more potent than [Met]enkephalin in the guinea pig ileum assay, which suggests that the adrenal enkephalin-containing peptide may perform a unique biological function in vivo.Proceedings of the National Academy of Sciences 06/1981; 78(5):3265-8. · 9.74 Impact Factor
- Proceedings of The National Academy of Sciences - PNAS. 01/1992;
- [show abstract] [hide abstract]
ABSTRACT: The opioid/orphanin gene family provides a model system for analyzing the outcomes of genome duplication events. Recent studies on the proenkephalin gene provide additional evidence that the organizational plan for this gene has been conserved throughout the extensive radiation of the gnathostome vertebrates. However, an analysis of the amino acid sequence of proenkephalin from the zebrafish, Danio rerio, suggests that novel forms of this opioid precursor may be evolving in teleosts. Analyses of sarcopterygian prodynorphin sequences revealed a proenkephalin signature in prodynorphin. Current studies on the opioid/orphanin gene family point to the duplication events that shaped this family occurring prior to the radiation of the gnathostomes.Annals of the New York Academy of Sciences 05/2005; 1040:22-37. · 4.38 Impact Factor