Structure of Ribulose 1,5-bisphosphate Carboxylase/Oxygenase Gene Cluster from a Thermophilic Hydrogen-Oxidizing Bacterium, Hydrogenophilus thermoluteolus, and Phylogeny of the Fructose 1,6-Bisphosphate Aldolase Encoded by cbbAin the Cluster

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.