HIGH-LEVEL EXPRESSION OF HUMAN ALPHA(S1)-CASEIN IN ESCHERICHIA-COLI

Human alpha(s1)-casein was expressed efficiently in Escherichia coli. The overproduced recombinant human alpha(s1)-casein was about 25% of t he total cell protein. Two different vectors were constructed to expre ss Met-alpha(s1)-casein and Met-alpha(s1)-casein with a His-affinity t ag at the C-terminus. Recombinant Met-alpha(s1)-casein with a His-affi nity tag was purified to homogeneity using Ni-nitrilotriacetic acid re sin. N-terminal sequence of the first 10 amino acid residues of this p urified protein was identical to that of mature human alpha(s1)-casein with an extra methionine residue at the N-terminus.