The cbbQ genes, located downstream of the form I and form II RubisCO genes, affect the activity of both RubisCOs

Hydrogenovibrio marinus strain MH-110, an obligately lithoautotrophic hydro gen-oxidizing bacterium, possesses three sets of the genes for ribulose 1,5 -bisphosphate carboxylase/oxygenase (RubisCO): namely, two form I type (cbb LS-1 and cbbLS-2) and one form II type (cbbM) enzymes. The cbbQ-m gene was located downstream of cbbM, and showed high similarity to other cbbQ genes and nirQ/norQ genes in denitrifying bacteria. Phylogenetic analysis of CbbQ and NirQ/NorQ indicated that CbbQ-m from Hv. marinus closely resembled Cbb Q from Thiobacillus intermedius and Thiobacillus neapolitannus and less clo sely resembled NirQ and NorQ. The cbbQ-m gene has been shown to activate th e form II RubisCO in E. coli cells, and the cbbQ-t from Hydrogenophilus the rmoluteolus could also activate the form II RubisCO. Both cbbQ genes have a lso been shown to activate the form I RubisCO from Hp. thermoluteolus in E. coli cells. However, the activation levels of two form I RubisCOs from Hv. marinus were smaller than that of form I RubisCOs from Hp. thermoluteolus, Form II RubisCO activated by CbbQ-m (QM) was purified from E. coli cells. The result of the 8-anilino-1-naphthalenesulfonate binding assay an the cir cular dichroism spectra indicated that QM was conformationally different fr om Form II RubisCO that was not activated by CbbQ. (C) 1999 Academic Press.