Complementary DNA cloning of a protein highly homologous to mammalian sarcoplasmic reticulum Ca-ATPase from the crustacean Artemia

Complementary DNA clones coding for an Artemia ATPase have been isolated using an oligonucleotide probe for a region highly conserved between P-type ATPases. The nucleotide sequence of three overlapping clones, 3309 base-pairs, has been established. This sequence includes 78 nucleotides of 5' untranslated sequence, an open reading frame of 3009 nucleotides and 222 nucleotides of 3' untranslated sequences. The amino acid sequence predicted for the coding region is 71% similar to that of slow and fast twitch rabbit muscle sarcoplasmic reticulum Ca-ATPases. The homology is specially high in some regions of the protein that include the previously described regions that are similar between all known P-type ATPases, as well as transmembrane domains and intra- and extracellular domains adjacent to the membrane that are not conserved in P-type ATPases but have been proposed to be involved in calcium binding and transport in rabbit sarcoplasmic reticulum Ca-ATPases. Probes of this likely sarcoplasmic reticulum Ca-ATPase hybridize to two mRNAs of 5200 and 4500 bases. Although both mRNAs are already present in cryptobiotic embryos, the levels of the 5200 base mRNA decrease after development is reassumed, being undetectable after hatching of the nauplii. The levels of the 4500 base mRNA increase during development; maximal levels are reached by ten hours and are maintained at later stages of development.