A DNA sequence encoding the human PRKAG1 (P54619) (Met 1-Pro 331), constructed the plasmid 1; A DNA sequence encoding the human PRKAB1 (Q9Y478) (Met 1-Ile 270), constructed the plasmid 2; A DNA sequence encoding the human PRKAA1 (Q13131-1) (Met 1-Gln 559) was fused with the N-terminal polyhistidine-tagged GST tag at the N-terminus, constructed the plasmid 3. The three plasmids were co-expressed and the heterotrimer was purifie.