Dna sequences encoding insulin precursors and methods of production

Abstract

DNA molecule and process for producing insulin precursors having the formula B(1-29) -H.sub.1 --X.sub.2 --Y.sub.2 --Y.sub.1 --A(1-21), wherein B(1-29) are the 29 first amino acid residues of the B chain of human insulin starting from the N-terminus, A(1-21) are the 21 amino acid residues of the A chain of human insulin, X.sub.1 represents a peptide bond or one naturally-occurring alpha-amino acid acid residues, X.sub.2 represents Glu or Asp, and Y.sub.1 and Y.sub.2 each represent Lys or Arg, the positions A6 and A11, A7 and B7 and A20 and B19, respectively, are connected through sulphur bridges, and, if desired, one or more of the glutamic acid residues in positions A4, A17, B13 and B21 are substituted by another naturally-occurring alpha-amino acid residue having an uncharged side chain, are provided. The insulin precursors are prepared by culturing a yeast strain transformed with a replicable plasmid comprising a DNA sequence encoding an insulin precursor of the above formula in a suitable medium and isolating the insulin precursor thus formed from the culture medium. The insulin precursor can be converted into human insulin or insulin analogues by enzymatic treatment in a manner known per se.