The covalent structure of pig kidney fructose-1,6-bisphosphatase. Sequence of a 63-residue cyanogen bromide peptide containing a phosphorylatable serine.

Native pig kidney fructose-1,6-bisphosphatase, in contrast to the rat liver enzyme, is not a substrate of cyclic AMP-dependent protein kinase. However, the pig kidney enzyme becomes a substrate when phosphorylation is performed in 1.6 M urea, after prior unfolding in 8 M urea. A cyanogen bromide fragment containing the phosphorylation site has been isolated and the amino acid sequence of this 63-residue peptide has been determined. This peptide has the following sequence: Leu-Asp-Pro-Ala-Ile-Gly-Glu-Phe-Ile-Leu-Val-Asp-Arg-Asn-Val-Lys-le-Lys-Lys-Lys- Gly-Ser(P)-Ile-Tyr-Ser-Ile-Asn-Glu-Gly-Tyr-Ala-Lys-Glu-Phe-Asp-Pro-Ala-Ile-Thr- Glu-Tyr-Ile-Glu-Arg-Lys-Lys-Phe-Pro-Pro-Asp-Asn-Ser-Ala-Pro-Tyr-Gly-Ala-Arg-Tyr -Val-Gly-Ser-Met. The amino acid sequence around the phosphorylated serine residue resembles those of other protein substrates of cyclic AMP-dependent protein kinase, but it is completely different from the phosphorylation site found in native rat liver fructose-1,6-bisphosphatase.