A Clostridium perfringens hem Gene Cluster Contains a cysGB Homologue That Is Involved in Cobalamin Biosynthesis

• Published in: MICROBIOLOGY and IMMUNOLOGY Vol. 43; no. 10; pp. 947 - 957
• Main Authors: Koyama, Michio, Katayama, Seiichi, Kaji, Masato, Taniguchi, Yuki, Matsushita, Osamu, Minami, Junzaburo, Morita, Shushi, Okabe, Akinobu
• Format: Journal Article
• Language: English
• Published: Tokyo Blackwell Publishing Ltd 01.10.1999; Center For Academic Publications Japan; Center for Academic Publications Japan
• Subjects: Bacteriology; Biological and medical sciences; Clostridium perfringens; Cobalamin biosynthesis; Fundamental and applied biological sciences. Psychology; Genetics; hem genes; Microbiology; Tetrapyrrole; Genetic mapping; Gene cluster; Nucleotide sequence; Operon; Clostridiales; Homology; Gene organization; Biosynthesis; Clostridium perfringens; Cyanocobalamin; Clostridiaceae; Bacteria; Cobalamine; Aminoacid sequence
• ISSN: 0385-5600; 1348-0421
• DOI: 10.1111/j.1348-0421.1999.tb03355.x

The hem gene cluster, which consists of hemA, cysGB, hemC, hemD, hemB, and hemL genes, and encodes enzymes involved in the biosynthetic pathway from glutamyl-tRNA to uroporphyrinogen III, has been identified by the cloning and sequencing of two overlapping DNA fragments from Clostridium perfringens NCTC8237. The deduced amino acid sequence of the N-terminal region of C. perfringens HemD is homologous to those reported for the C-terminal region of Salmonella typhimurium CysG and Clostridium josui HemD. C. perfringens CysGB is a predicted 220-residue protein which shows homology to the N-terminal region of S. typhimurium CysG. Disruption of the cysGB gene in C. perfringens strain 13 by homologous recombination reduced cobalamin (vitamin B12) levels by a factor of 200. When grown in vitamin B12-deficient medium, the mutant strain showed a four-fold increase in its doubling time compared with that of the wild-type strain, and this effect was counteracted by supplementing the medium with vitamin B12. These results suggest that C. perfringens CysGB is involved in the chelation of cobalt to precorrin II as suggested for the CysGB domain of S. typhimurium CysG, enabling the synthesis of cobalamin.