Presence of duplicate genes encoding a phylogenetically new subgroup of form I ribulose 1,5-bisphosphate carboxylase/oxygenase in Mycobacterium sp. strain JC1 DSM 3803

Ribulose 1,5-bisphosphate carboxylase/oxygenase (RubisCO) is the key enzyme of the Calvin reductive pentose phosphate cycle. Two sets of the structural genes for form I RubisCO were identified in Mycobacterium sp. strain JC1. The genes were clustered on the chromosome in the transcriptional order of cbbL-cbbS. Cloned cbbL-1 and cbbS-1 and cbbL-2 and cbbS-2 have open reading frames of 1431, 426, 1428, and 426 nucleotides, respectively. Primer extension analysis revealed that transcriptional start sites of cbbLS-1 and -2 genes were the nucleotides T and G located 99 and 41 bp upstream of the cbbL start codons, respectively. CbbLS-1 and CbbLS-2 that were expressed in Escherichia coli exhibited RubisCO activity. A phylogeny of CbbL amino acid sequences revealed that the two enzymes in Mycobacterium sp. strain JC1 may form a new phylogenetic subgroup, type IE, in the 'red-like' group of the form I RubisCO family.