title: A possible molecular ancestor for mollusk APGWamide, insect adipokinetic hormone, and crustacean red pigment concentrating hormone.
abstract: Precursor structures of various members of the neuropeptide family adipokinetic hormone/red pigment concentrating hormone (AKH/RPCH) of mandibular arthropods and the APGWamide family of mollusks were compared. Amino acid alignments showed a common overall architecture (signal peptide, active peptide, related peptide), with a similar alpha helix-random coil secondary structure. DNA sequence alignments revealed close similarities between the genes encoding for the peptides of the two families. The APGWamide genes are larger than the AKH/RPCH genes. The sequence environment occupied by introns is similar in AKH/RPCH and APGWamide genes. Such similarities suggest that these peptide families might have been originated by gene rearrangements from a common ancestor having either an AKH/RPCH/APGWamide-like structure or both an AKH/RPCH-like and an APGWamide-like structures. In the former model, DNA fragments could have been gained when the ancestor evolved to mollusks and it could have lost nucleotides when the progression to mandibular arthropods took place. In the second model, AKH/RPCH-like structures could have been fused during evolution toward mandibular arthropods, whereas in mollusks they could have been lost with the possible amplification of the APGWamide-like structure. Loss of domains in exon 1 may have originated the signal peptide and the first codon of the active RPCH. In exon 2, loss of domains possibly determined the junctions of codons 2 to 5 with the loss of a APGWamide copy; exon 3 underwent fewer variations. The similarity of the mollusk APGWamide precursors is closer to that of the RPCH family than the insect AKH family, indicating an earlier evolutionary departure.
authors.affiliation: Posgrado en Ciencias Biológicas, Facultad de Ciencias, Universidad Nacional Autónoma de México, México, D.F., México.
authors.forename: Francisco
authors.initials: F
authors.lastname: Martínez-Pérez
authors.forename: Arturo
authors.initials: A
authors.lastname: Becerra
authors.forename: Jesús
authors.initials: J
authors.lastname: Valdés
authors.forename: Samuel
authors.initials: S
authors.lastname: Zinker
authors.forename: Hugo
authors.initials: H
authors.lastname: Aréchiga
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D004247:DNA; D019143:Evolution, Molecular; D014644:Genetic Variation; D006110:Grasshoppers; D007301:Insect Hormones / Q000235:genetics*; D008969:Molecular Sequence Data; D009479:Neuropeptides / Q000235:genetics*; D009842:Oligopeptides / Q000235:genetics*; D011498:Protein Precursors / Q000235:genetics; D011761:Pyrrolidonecarboxylic Acid / Q000031:analogs & derivatives; D016415:Sequence Alignment
chemical_list: D007301:Insect Hormones; D009479:Neuropeptides; D009842:Oligopeptides; D011498:Protein Precursors; C044833:adipokinetic hormone; C063193:alanyl-prolyl-glycyl-tryptophanamide; C022059:red pigment-concentrating hormone; D004247:DNA; D011761:Pyrrolidonecarboxylic Acid