Cloning and expression of sarco/endoplasmic reticulum CA²⁺-ATPase of crayfish procambarus clarkii

A full-length cDNA en coding crayfish muscle sarco/endoplasmic reticulum Ca²⁺-ATPase (SERCA) has been cloned using RT-PCR. The nucleotide sequence of this 3856 bp clone has been established. It includes 145 nucleotides non-coding region at the 5' end, an open reading frame of 3006 nucleotides and 705 nucleotides of 3' untranslated sequence. The amino acid sequence predicted from the coding region is 79% identical to that of SERCA of another crustacean, Artemia and 77% identical to that of rabbit fast-twitch muscle SERCA. A 460 bp DNA fragment of this likely SERCA was used as a probe of a Northern blot of mRNA from a variety of crayfish tissues. In muscle and antennal gland (kidney), three transcripts of 5.8 kb, 9.0 kb and 10.1 kb were recognized by this probe. In gill, the 9.0 kb band was replaced by an 8.1 kb band. These results indicated four possible isoforms of SERCA. Quantification of expression by slot-blot showed that muscle SERCA mRNA in premolt and postmolt decreased respectively to 53% (P < 0.02) and 43% (P < 0.002) of the intermolt expression, indicating possible regulation during the molting cycle.