The co-expression in Escherichia coli of the gamma-subunit and the catalytic alpha-subunit of the thermostable glucose dehydrogenase (GDH) from Burkholderia cepacia sp. SM4 produced 12.7 U GDH activity mg(-1) protein. A 47-amino acid, twin-arginine translocase signal peptide was identified at the amino terminus of the gamma-subunit. The expression of the alpha-subunit in the absence of the gamma-subunit or the gamma-subunit signal peptide failed to produce any detectable GDH protein or activity. The gamma-subunit may be a chaperone-like component that assists folding of the alpha-subunit polypeptide to the active form and its translocation to the periplasm.