Regulatory system of the protocatechuate 4,5-cleavage pathway genes essential for lignin downstream catabolism.
Sphingobium sp. strain SYK-6 converts various lignin-derived biaryls with guaiacyl (4-hydroxy-3-methoxyphenyl) and syringyl (4-hydroxy-3,5-dimethoxyphenyl) moieties to vanillate and syringate. These compounds are further catabolized through the protocatechuate (PCA) 4,5-cleavage (PCA45) pathway. In this article, the regulatory system of the PCA45 pathway is described. A LysR-type transcriptional regulator (LTTR), LigR, activated the transcription of the ligK-orf1-ligI-lsdA and ligJABC operons in the presence of PCA or gallate (GA), which is an intermediate metabolite of vanillate or syringate, respectively, and repressed transcription of its own gene. LigR bound to the positions -77 to -51 and -80 to -48 of the ligK and ligJ promoters, respectively, and induced DNA bending. In the presence of PCA or GA, DNA bending on both promoters was enhanced. The LigR-binding regions of the ligK and ligJ promoters in the presence of inducer molecules were extended and shortened, respectively. The LTTR consensus sequences (Box-K and Box-J) in the ligK and ligJ promoters were essential for the binding of LigR and transcriptional activation of both operons. In addition, the regions between the LigR binding boxes and the -35 regions were required for the enhancement of DNA bending, although the binding of LigR to the -35 region of the ligJ promoter was not observed in DNase I footprinting experiments. This study shows the binding features of LigR on the ligK and ligJ promoters and explains how the PCA45 pathway genes are expressed during degradation of lignin-derived biaryls by this bacterium.
Kamimura
Naofumi
N
Department of Bioengineering, Nagaoka University of Technology, Nagaoka, Niigata 940-2188, Japan.
Takamura
Kazuhiro
K
Hara
Hirofumi
H
Kasai
Daisuke
D
Natsume
Ryo
R
Senda
Toshiya
T
Katayama
Yoshihiro
Y
Fukuda
Masao
M
Masai
Eiji
E
D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D018983:DNA Footprinting; D003850:Deoxyribonuclease I; D024202:Electrophoretic Mobility Shift Assay; D005707:Gallic Acid / Q000031:analogs & derivatives / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D062385:Hydroxybenzoates / Q000378:metabolism*; D008031:Lignin / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000235:genetics / Q000502:physiology; D042301:Sphingomonadaceae / Q000235:genetics / Q000378:metabolism*; D014641:Vanillic Acid / Q000378:metabolism
D001426:Bacterial Proteins; D062385:Hydroxybenzoates; C009091:protocatechuic acid; D005707:Gallic Acid; D008031:Lignin; C001945:syringic acid; D003850:Deoxyribonuclease I; D014641:Vanillic Acid