5′‐Methylbenzimidazolyl‐cobamides are the corrinoids from some sulfate‐reducing and sulfur‐metabolizing bacteria

Abstract

The sulfate-reducing bacteria Desulfobacteriurn autotrophicum, Desulfobulbus propionicus and Archaeoglobus fulgidus and the sulfur-metabolizing archaebacteria Desulfurolobus ambivalens and Thermoplasma acidophilum were found to contain considerable amounts of corrinoids, that were isolated and crystallized in their COB-cyano form. In three other sulfur-metabolizing archaebacteria, Thermoproteus neutrophilus, Pyrodictium occultum and Staphylothermus marinus significant amounts of corrinoids were not detected under the isolation methods used.The samples from the three sulfate-reducers were identified with Co,-[a-(5'-methylbenzimidazolyl)]-Copcyanocobamide. This corrinoid was also obtained from a 5-methylbenzimidazole-supplemented Propionibacterium fermentation and was structurally characterized by ultraviolet/visible, CD, fast-atom-bombardment MS, 'H-and 13C-NMR spectroscopy. Also the major corrinoid from T. acidophilum was (tentatively) analyzed as a 5'-methylbenzimidazolyl-cobamide, whereas the main corrinoid from D. ambivalens was indicated to be vitamin B12 (a 5',6'-dimethylbenzimidazolyl-cobamide).The 5'-methylbenzimidazolylcobamides are found here as the common corrins of some sulfate-reducing and sulfur-metabolizing bacteria. The structural diversity due to the differing nucleotide bases of the corrins examined here and in methanogenic and acetogenic bacteria appears not to correlate to the biological function(s) of the corrins, but rather to be determined by biosynthetic properties of these organisms under natural growth conditions. Vitamin B12 derivatives are perhaps one of the most broadly distributed forms of the pyrrolic compounds in (both) the eubacterial and archaebacterial kingdoms and presumably also are among the phylogenetic oldest [l, 21. Corrinoids have been found in high levels in methanogenic and acetogenic bacteria in particular, in some cases amounting to more than 0.1 % of the total bacterial dry mass [3, 41. To date, the natural corrins have been shown to provide several metabolically important organometallic cofactors: as Cop-deoxyadenosyl-cobamides (such as coenzyme B 2 , 1) they catalyze enzymatic rearrangements and ribonucleotide reductions [S, 61, and as Cos-methyl-cobamides (such as methyl-cobalamin, 2) they act in methyl-group-transfer reactions [7, 81. In addition, they have been suggested recently to function as electron-transfer redox catalysts in the energyconserving formation of CH4 in methanogenic bacteria [9 -111, presumably involving complete Co(I1)-and Co(1)-corrins, that lack an axial ligand on the b-face of the corrin-bound cobalt ion [8].The corrinoids are thus recognized to differ by the structure of their Cos ligands according to their biological function

Structural Investigation of the Biosynthesis of Alternative Lower Ligands for Cobamides by Nicotinate Mononucleotide: 5,6-Dimethylbenzimidazole Phosphoribosyltransferase from Salmonella enterica

“…Significantly, the 5-methyl-substituted product is generated in the crystal lattice as seen in natural cobamides (30). This suggests that the substrate binding pocket has a higher affinity for the methyl group in the 5-position than in the rotated position that would yield the 6-methyl product.…”

“…5-Methylbenzimidazole-5-Methylbenzimidazole is the lower ligand in microorganisms such as Desulfobulbus autotrophicum, Desulfobulbus propionicus, and Archaeoglobus fulgidus (30). Crystals soaked in 1.9 mM 5-methylbenzimidazole show unambiguous electron density for this ligand (Fig.…”

Unexpected Specificity of Interspecies Cobamide Transfer from Geobacter spp. to Organohalide-Respiring Dehalococcoides mccartyi Strains

“…For example, methanogens and acetogens synthesize methylcobamides or other vitamin B 12 analogues to assemble functional corrinoid-dependent methyltransferases that catalyze methyl transfer reactions crucial for methanogenesis and acetogenesis (19,23). Sulfate reducers, such as Desulfobacterium autotrophicum and Desulfobulbus propionicus, synthesize 5=-methylbenzimidazolyl-cobamide, a required cofactor in the acetyl coenzyme A pathway for CO 2 fixation and acetate oxidization (17).…”

ABC Transporter for Corrinoids inHalobacteriumsp. Strain NRC-1

“…Cobamides have been isolated with the lower ligand 5-methylbenzimidazole from Archaeoglobus fulgidus and T. acidophilum (23), adenine from Methanosarcina barkeri (35), and 5-hydroxybenzimidazole from M. marburgensis strain Marburg (24). It appears that the differences between the cobamides made by different species of prokaryotes correlate not with the biological functions of the cobamide but with the metabolic conditions of the organism in its natural habitat (23).…”