title: Evolution of tissue-specific keratins as deduced from novel cDNA sequences of the lungfish Protopterus aethiopicus.
abstract: Lungfishes are possibly the closest extant relatives of the land vertebrates (tetrapods). We report here the cDNA and predicted amino acid sequences of 13 different keratins (ten type I and three type II) of the lungfish Protopterus aethiopicus. These keratins include the orthologs of human K8 and K18. The lungfish keratins were also identified in tissue extracts using two-dimensional polyacrylamide gel electrophoresis, keratin blot binding assays and immunoblotting. The identified keratin spots were analyzed by peptide mass fingerprinting which assigned seven sequences (inclusively Protopterus K8 and K18) to their respective protein spot. The peptide mass fingerprints also revealed the fact that the major epidermal type I and type II keratins of this lungfish have not yet been sequenced. Nevertheless, phylogenetic trees constructed from multiple sequence alignments of keratins from lungfish and distantly related vertebrates such as lamprey, shark, trout, frog, and human reveal new insights into the evolution of K8 and K18, and unravel a variety of independent keratin radiation events.
authors.affiliation: Institut für Zoologie, Johannes Gutenberg-Universität, Mallerweg 6, D-55099 Mainz, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Schaffeld
authors.forename: Miriam
authors.initials: M
authors.lastname: Bremer
authors.forename: Christian
authors.initials: C
authors.lastname: Hunzinger
authors.forename: Jürgen
authors.initials: J
authors.lastname: Markl
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D018076:DNA, Complementary; D015180:Electrophoresis, Gel, Two-Dimensional; D019143:Evolution, Molecular; D005399:Fishes / Q000235:genetics*; D005455:Fluorescent Antibody Technique; D007633:Keratins / Q000737:chemistry / Q000235:genetics*; D008969:Molecular Sequence Data; D010449:Peptide Mapping; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
chemical_list: D018076:DNA, Complementary; D007633:Keratins