title: Cloning and expression of mitochondrial and protoflagellar creatine kinases from a marine sponge: implications for the origin of intracellular energy transport systems.
abstract: Creatine kinase (CK) plays a central role in energy transactions in cells displaying high and variable rates of ATP turnover. Cytoplasmic and mitochondrial CK genes code for isoforms which are targeted to distinct intracellular compartments often in close physical proximity to sites of ATP hydrolysis or synthesis. In certain lower groups a third CK gene is present which codes for a flagellar CK isoform consisting of three complete, fused CK domains. Recent work has shown that cytoplasmic, mitochondrial, and flagellar CKs are present in protochordates and in deuterostome and protostome invertebrates. We report here that the marine sponge Tethya aurantia, a representative of the oldest of all multi-cellular animal groups, expresses three unique CK transcripts. One of these CK transcripts codes for protein that has a mitochondrial targeting sequence and in a phylogenetic analysis is positioned at the base of the cluster containing mitochondrial CK sequences from invertebrates, protochordates, and vertebrates; it is clearly a mitochondrial CK. When expressed in Escherichia coli the mitochondrial form from T. aurantia was found to be dimeric unlike all other mitochondrial CKs which are typically octameric. The other two T. aurantia transcripts code for proteins that appear to be more closely related to flagellar CKs. These protoflagellar CKs were found to be dimers when expressed in Escherichia coli. Sponges last shared a common ancestor with higher animals as long as one billion years ago. The antiquity of intracellular localization, as evidenced by the presence of a true mitochondrial CK and protoflagellar CKs in the sponge T. aurantia, indicates that physical constraints on cellular energy transport were key, early driving forces in the evolution of this key enzyme system.
authors.affiliation: Institute of Molecular Biophysics and Department of Biological Science, Florida State University, Tallahassee, FL 32306-4370, USA.
authors.forename: Sona
authors.initials: S
authors.lastname: Sona
authors.forename: Tomohiko
authors.initials: T
authors.lastname: Suzuki
authors.forename: W Ross
authors.initials: WR
authors.lastname: Ellington
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001692:Biological Transport; D002938:Ciona intestinalis / Q000201:enzymology; D003001:Cloning, Molecular; D003402:Creatine Kinase / Q000096:biosynthesis* / Q000737:chemistry / Q000235:genetics*; D003593:Cytoplasm / Q000201:enzymology*; D019281:Dimerization; D004734:Energy Metabolism; D004926:Escherichia coli / Q000378:metabolism; D007527:Isoenzymes; D051379:Mice; D008928:Mitochondria / Q000201:enzymology*; D008969:Molecular Sequence Data; D010802:Phylogeny; D011077:Polychaeta / Q000201:enzymology; D011161:Porifera / Q000201:enzymology*; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid
chemical_list: D007527:Isoenzymes; D011994:Recombinant Proteins; D003402:Creatine Kinase