PCR AMPLIFICATION AND CLONING OF METALLOTHIONEIN COMPLEMENTARY DNAS IN TEMPERATE AND ANTARCTIC SEA-URCHIN CHARACTERIZED BY A LARGE DIFFERENCE IN EGG METALLOTHIONEIN CONTENT

Metallothionein levels were determined in the eggs of two sea urchin s pecies, the Mediterranean Sphaerechinus granularis and the Antarctic S terechinus neumayeri. While appreciable levels of metallothionein were found in S. granularis eggs, a negligible amount was detected in S. n eumayeri. Two metallothionein isoforms were purified from S. granulari s. and metallothionein cDNAs were obtained by means of reverse transcr iptase-polymerase chain reaction (RT-PCR). Two distinct cDNA species w ere cloned and sequenced. The translated amino acid sequences of these two forms consisted of 67 residues and differed in two amino acid sub stitutions. Despite the lack of metallothionein in S. neumayeri eggs, a metallothionein cDNA was obtained by RT-PCR amplification and a sing le amino acid sequence coding for a 63 residues MT was deduced. A comp arative analysis of the primary structure of S. granularis and S. neum ayeri metallothioneins with those of the other sea urchin metallothion eins has been performed. Sea urchin metallothioneins appear to be less similar to each other than metallothioneins of closely related verteb rates.