The present invention discloses the isolation and use of a specific bacterial promoter region suitable for use in constructs for the high level production of heterologous proteins. This promoter is derived from the bacterial gene encoding for alcohol dehydrogenase, in particular the alcohol dehydrogenase genes isolated from the thermophilic bacterial strain T. brockii and the mesophilic bacterial strain Clostridium beijerinckii. It is now disclosed that using either the intact promoter region or certain specific fragments consisting of at least a 88 bp DNA sequence in the upstream untranslated region of the bacterial alcohol dehydrogenase gene, operatively linked to the nucleic acid sequences encoding a heterologous protein, and insertion into a DNA plasmid or any other suitable vector system, heterologous genes can be expressed in high levels in host cells. Heterologous proteins or peptides can be expressed constitutively at high levels. The proteins are obtained in their active folded form.