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The cbbRencoding the LysR‐type transcriptional regulator is located downstream of cbbLSQOYAand this gene is located upstream of cbbFPTin divergent transcription. The two promoter regions with LysR‐binding sites are located in the cbbLupstream region and in the cbbR–cbbFintergenic region. Electrophoretic mobility shift assays using a cell extract of Escherichia coliharboring a plasmid containing cbbRand the DNA fragments of promoter regions indicated that CbbR binds in both regions. NADPH caused differences in the complex of CbbR and DNA.

Four genes, cbbO, cbbY, cbbA, and the pyruvate kinase gene (pyk), were found downstream of ribulose 1,5-bisphosphate carboxylase/oxygenase (RubisCO) genes, cbbLS, from a thermophilic hydrogen-oxidizing bacterium, Hydrogenophilus thermoluteolus(formerly Pseudomonas hydrogenothermophila). cbbOwas similar to norDin the denitrification gene cluster, and cbbYwas similar to cbbYfrom other autotrophic bacteria. cbbAencoded fructose 1,6-bisphosphate aldolase (FBP aldolase); however, CbbA was little similar to other CbbA proteins. When CbbA was overexpressed in Escherichia coli, overproduction of CbbA was detected by SDS-PAGE. However, the cell extract had slightly higher activity than a cell extract of E. coliwithout cbbA. Phylogenetic analysis showed class II FBP aldolase divided into classes IIA and IIB, and that CbbA from H. thermoluteoluswas in class IIA. Activities of RubisCO and FBP aldolase were examined under autotrophic, mixotrophic, and heterotrophic conditions. The activities of the two enzymes were regulated independently.

Hydrogenovibrio marinusstrain MH-110, an obligately lithoautotrophic hydrogen-oxidizing bacterium, possesses three sets of the genes for ribulose 1,5-bisphosphate carboxylase/oxygenase (RubisCO): namely, two form I type (cbbLS-1and cbbLS-2) and one form II type (cbbM) enzymes. The cbbQ-mgene was located downstream of cbbM,and showed high similarity to other cbbQgenes and nirQ/norQgenes in denitrifying bacteria. Phylogenetic analysis of CbbQ and NirQ/NorQ indicated that CbbQ-m from Hv. marinusclosely resembled CbbQ from Thiobacillus intermediusand Thiobacillus neapolitannusand less closely resembled NirQ and NorQ. The cbbQ-mgene has been shown to activate the form II RubisCO in E. colicells, and the cbbQ-tfrom Hydrogenophilus thermoluteoluscould also activate the form II RubisCO. Both cbbQgenes have also been shown to activate the form I RubisCO from Hp. thermoluteolusin E. colicells. However, the activation levels of two form I RubisCOs from Hv. marinuswere smaller than that of form I RubisCOs from Hp. thermoluteolus.Form II RubisCO activated by CbbQ-m (QM) was purified from E. colicells. The result of the 8-anilino-1-naphthalenesulfonate binding assay and the circular dichroism spectra indicated that QM was conformationally different from Form II RubisCO that was not activated by CbbQ.

The cbbR encoding the LysR-type transcriptional regulator is located downstream of cbbLSQOYA and this gene is located upstream of cbbFPT in divergent transcription. The two promoter regions with LysR-binding sites are located in the cbbL upstream region and in the cbbR –cbbF intergenic region. Electrophoretic mobility shift assays using a cell extract of Escherichia coli harboring a plasmid containing cbbR and the DNA fragments of promoter regions indicated that CbbR binds in both regions. NADPH caused differences in the complex of CbbR and DNA.