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Cloning and expression in Escherichia coli of a dog thyroid cDNA encoding a novel inositol 1,4,5-trisphosphate 5-phosphatase

par Verjans, Benoît ;De Smedt, Florence ;Lecocq, Raymond ;Vanweyenberg, Valérie ;Moreau, Colette ;Erneux, Christophe
Référence Biochemical journal, 300, 1, page (85-90)
Publication Publié, 1994

Article révisé par les pairs

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Résumé :

In brain and many other tissues, type I inositol 1,4,5-trisphosphate (InsP3) 5-phosphatase is the major isoenzyme hydrolysing the calcium-mobilizing second messenger InsP3. This protein has been purified to apparent homogeneity from a crude soluble fraction of bovine brain, yielding a single major protein band with a molecular mass of 43 kDa after SDS/PAGE. This material was used to determine internal microsequences. A partial DNA sequence has been amplified by PCR by using degenerate primers deduced from two protein sequences (FKAKKYKKV and DENYKSQE). A cDNA clone (BVCT) was isolated by screening a dog thyroid cDNA library. The encoded protein of 412 amino acids has a calculated molecular mass of 47681 Da. Peptide sequences generated from the bovine brain enzyme were found to be 96% conserved compared with the dog thyroid protein. When clone BVCT was expressed in Escherichia coli, the recombinant protein was shown to hydrolyse both InsP3 and inositol 1,3,4,5-tetrakisphosphate, with apparent K(m) values of 28 and 3 μM respectively. Enzyme activity was inhibited by EDTA and 2,3-bisphosphoglycerate, both inhibitors of native InsP3 5-phosphatase, but not by EGTA and LiCl, as previously shown for the bovine brain enzyme. Our data show the cloning of type I InsP3 5-phosphatase which, interestingly does not share any significant sequence identity with the previously cloned type III isoenzyme.