Origin and properties of cytoplasmic and mitochondrial isoforms of taurocyamine kinase

Abstract

Taurocyamine kinase (TK) is a member of the highly conserved family of phosphagen kinases that includes creatine kinase (CK) and arginine kinase. TK is found only in certain marine annelids. In this study we used PCR to amplify two cDNAs coding for TKs from the polychaete Arenicola brasiliensis, cloned these cDNAs into the pMAL plasmid and expressed the TKs as fusion proteins with the maltose-binding protein. These are the first TK cDNA and deduced amino acid sequences to be reported. One of the two cDNA-derived amino acid sequences of TKs shows a high amino acid identity to lombricine kinase, another phosphagen kinase unique to annelids, and appears to be a cytoplasmic isoform. The other sequence appears to be a mitochondrial isoform; it has a long N-terminal extension that was judged to be a mitochondrial targeting peptide by several on-line programs and shows a higher similarity in amino acid sequence to mitochondrial creatine kinases from both vertebrates and invertebrates. The recombinant cytoplasmic TK showed activity for the substrates taurocyamine and lombricine (9% of that of taurocyamine). However, the mitochondrial TK showed activity for taurocyamine, lombricine (30% of that of taurocyamine) and glycocyamine (7% of that of taurocyamine). Neither TK catalyzed the phosphorylation of creatine. Comparison of the deduced amino acid sequences of mitochondrial CK and TK indicated that several key residues required for CK activity are lacking in the mitochondrial TK sequence. Homology models for both cytoplasmic and mitochondrial TK, constructed using CK templates, provided some insight into the structural correlation of differences in substrate specificity between the two TKs. A phylogenetic analysis using amino acid sequences from a broad spectrum of phosphagen kinases showed that annelid-specific phosphagen kinases (lombricine kinase, glycocyamine kinase and cytoplasmic and mitochondrial TKs) are grouped in one cluster, and form a sister-group with CK sequences from vertebrate and invertebrate groups. It appears that the annelid-specific phosphagen kinases, including cytoplasmic and mitochondrial TKs, evolved from a CK-like ancestor(s) early in the divergence of the protostome metazoans. Furthermore, our results suggest that the cytoplasmic and mitochondrial isoforms of TK evolved independently.Abbreviations

Hypotaurocyamine kinase evolved from a gene for arginine kinase

“…Phylogenetic analyses have shown two major evolutionary lineages among the phosphagen kinases, CK and AK, which likely diverged at the dawn of the radiation of multi-cellular animals [10]. The available evidence suggests that GK, TK, and LK evolved within the CK lineage, most likely after the divergence of the lophotrochozoan and ecdysozoan protostomes [7,9,31]. However, the phylogenetic position of HTK remains to be determined.…”

“…Comparison of the available CK, AK, GK, TK and LK sequences suggest their evolution from a common ancestor [6][7][8][9], although these relationships are not fully understood. Phylogenetic analyses have shown two major evolutionary lineages among the phosphagen kinases, CK and AK, which likely diverged at the dawn of the radiation of multi-cellular animals [10].…”

Variable intron/exon structure in the oligochaete lombricine kinase gene

“…The CK branch underwent early evolutionary modification via gene duplication and divergence and proteins evolved with similar functions but with different substrate preferences. Phylogenetic analysis strongly indicates that glycocyamine kinases (GKs), lombricine kinases (LKs), and taurocyamine kinases (TKs) evolved from a CK-like ancestor Suzuki et al, 1997;Uda et al, 2005). Just like CK, these enzymes are typically oligomeric, which may facilitate targeting and localization within cells.…”

Cold-adapted Features of Arginine Kinase from the Deep-sea Clam Calyptogena kaikoi

“…Previously, we reported that deep-sea invertebrates Riftia pachyptila and Calyptogena kaikoi contain taurocyamine kinase (Uda et al 2005) and AK (Uda et al 2008), respectively. Since C. kaikoi, living in the cold-seep area at depths >3,500 m in the Nankai Trough, Japan, is a psychrophilic species, its enzyme can be used as model to elucidate cold-adapted strategy for deep-sea invertebrates.…”