Biotechnology and Bioprocess Engineering 2021; 26(4): 612-620  
In vivo Characterization of the Inducible Promoter System of 3-hydroxypropionic Dehydrogenase in Pseudomonas denitrificans
Trinh Thi Nguyen, Nam Hoai Nguyen, Yeonhee Kim, Jung Rae Kim, and Sunghoon Park
Trinh Thi Nguyen, Yeonhee Kim, Sunghoon Park*
School of Energy and Chemical Engineering, UNIST, Ulsan 44919, Korea
Tel: +82-52-217-2565; Fax: +82-52-217-2309
Trinh Thi Nguyen, Jung Rae Kim, Sunghoon Park
School of Chemical and Biomolecular Engineering, Pusan National University, Busan 46241, Korea
Nam Hoai Nguyen
NOROO Bio R&D Center, NOROO Holdings Co., Ltd, Suwon 16229, Korea
Co-first authors
Received: September 8, 2020; Revised: October 7, 2020; Accepted: October 9, 2020; Published online: August 30, 2021.
© The Korean Society for Biotechnology and Bioengineering. All rights reserved.

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License ( which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Here, we characterized a gene expression system induced by 3-hydroxy propionic acid (3-HP) in Pseudomonas denitrificans. The system consists of a putative LysR-type transcriptional regulator (LTTR) encoded by hpdR and a LTTR-responsive promoter that positively controls the expression of hpdH, encoding 3-HP dehydrogenase in the presence of 3-HP. In the hpdH-responsive promoter region, two operators exhibiting dyad symmetry and designated O1 and O2 and centered at the -73 and -30 positions, respectively, were located upstream of the hpdH transcription start site. When either O1, O2, or both regions were mutated, the inducibility by the HpdR-3-HP complex was significantly reduced or completely removed, indicating that both sites are required for transcriptional activation. The HpdR protein and its operator sites on hpdH were highly specific for each other, and did not engage in cross-talk with another similar 3-HP-inducible system that is also present in P. denitrificans. This 3-HP-inducible promoter system should be useful in developing biosensors for 3-HP, and/or dynamic gene expression systems for metabolic engineering purposes.
Keywords: 3-hydroxpropionic acid (3-HP), 3-HP-inducible promoter system, LysR-type transcriptional regulator, LTTR-responsive promoter, 3-HP biosensor

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